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Golang gin-gonic Documentation

Este no es un post, de hecho el documento que se pone a continuación no es creado por mí sino por los creadores de gin-gonic. No necesariamente es para usted, pero puede serle de utilidad.

La documentación oficial se encuentra en https://github.com/gin-gonic/gin/blob/master/docs/doc.md. Fecha de subida 19/06/2023

Esta documentación no será traducida y Por el momento no se hará ningún tutorial a partir de ella

Esta documentación solo está aquí por el hecho que se me complico obtenerla:

contenido
Puedes cerrar o abrir este menú cliqueando sobre el boton contenido

Gin Quick Start

Build tags

https://blastcoding.com/golang-gin-gonic-documentation/#build-tags

Build with json replacement

https://blastcoding.com/golang-gin-gonic-documentation/#build-with-json-replacement

Gin uses encoding/json as default json package but you can change it by build from other tags.

jsoniter

go build -tags=jsoniter .

go-json

go build -tags=go_json .

sonic (you have to ensure that your cpu support avx instruction.)

$ go build -tags="sonic avx" .

Build without MsgPack rendering feature

https://blastcoding.com/golang-gin-gonic-documentation/#build-without-msgpack-rendering-feature

Gin enables MsgPack rendering feature by default. But you can disable this feature by specifying nomsgpack build tag.

go build -tags=nomsgpack .

This is useful to reduce the binary size of executable files. See the detail information.

API Examples

https://blastcoding.com/golang-gin-gonic-documentation/#api-examples

You can find a number of ready-to-run examples at Gin examples repository.

Using GET, POST, PUT, PATCH, DELETE and OPTIONS

https://blastcoding.com/golang-gin-gonic-documentation/#using-get-post-put-patch-delete-and-options 
func main() {
  // Creates a gin router with default middleware:
  // logger and recovery (crash-free) middleware
  router := gin.Default()

  router.GET("/someGet", getting)
  router.POST("/somePost", posting)
  router.PUT("/somePut", putting)
  router.DELETE("/someDelete", deleting)
  router.PATCH("/somePatch", patching)
  router.HEAD("/someHead", head)
  router.OPTIONS("/someOptions", options)

  // By default it serves on :8080 unless a
  // PORT environment variable was defined.
  router.Run()
  // router.Run(":3000") for a hard coded port
}

Parameters in path

https://blastcoding.com/golang-gin-gonic-documentation/#parameters-in-path 
func main() {
  router := gin.Default()

  // This handler will match /user/john but will not match /user/ or /user
  router.GET("/user/:name", func(c *gin.Context) {
    name := c.Param("name")
    c.String(http.StatusOK, "Hello %s", name)
  })

  // However, this one will match /user/john/ and also /user/john/send
  // If no other routers match /user/john, it will redirect to /user/john/
  router.GET("/user/:name/*action", func(c *gin.Context) {
    name := c.Param("name")
    action := c.Param("action")
    message := name + " is " + action
    c.String(http.StatusOK, message)
  })

  // For each matched request Context will hold the route definition
  router.POST("/user/:name/*action", func(c *gin.Context) {
    b := c.FullPath() == "/user/:name/*action" // true
    c.String(http.StatusOK, "%t", b)
  })

  // This handler will add a new router for /user/groups.
  // Exact routes are resolved before param routes, regardless of the order they were defined.
  // Routes starting with /user/groups are never interpreted as /user/:name/... routes
  router.GET("/user/groups", func(c *gin.Context) {
    c.String(http.StatusOK, "The available groups are [...]")
  })

  router.Run(":8080")
}

Querystring parameters

https://blastcoding.com/golang-gin-gonic-documentation/#querystring-parameters 
func main() {
  router := gin.Default()

  // Query string parameters are parsed using the existing underlying request object.
  // The request responds to an url matching:  /welcome?firstname=Jane&lastname=Doe
  router.GET("/welcome", func(c *gin.Context) {
    firstname := c.DefaultQuery("firstname", "Guest")
    lastname := c.Query("lastname") // shortcut for c.Request.URL.Query().Get("lastname")

    c.String(http.StatusOK, "Hello %s %s", firstname, lastname)
  })
  router.Run(":8080")
}

Multipart/Urlencoded Form

https://blastcoding.com/golang-gin-gonic-documentation/#multiparturlencoded-form 
func main() {
  router := gin.Default()

  router.POST("/form_post", func(c *gin.Context) {
    message := c.PostForm("message")
    nick := c.DefaultPostForm("nick", "anonymous")

    c.JSON(http.StatusOK, gin.H{
      "status":  "posted",
      "message": message,
      "nick":    nick,
    })
  })
  router.Run(":8080")
}

Another example: query + post form

https://blastcoding.com/golang-gin-gonic-documentation/#another-example-query–post-form
http response 
POST /post?id=1234&page=1 HTTP/1.1
Content-Type: application/x-www-form-urlencoded

name=manu&message=this_is_great

func main() {
  router := gin.Default()

  router.POST("/post", func(c *gin.Context) {

    id := c.Query("id")
    page := c.DefaultQuery("page", "0")
    name := c.PostForm("name")
    message := c.PostForm("message")

    fmt.Printf("id: %s; page: %s; name: %s; message: %s", id, page, name, message)
  })
  router.Run(":8080")
}
id: 1234; page: 1; name: manu; message: this_is_great

Map as querystring or postform parameters

https://blastcoding.com/golang-gin-gonic-documentation/#map-as-querystring-or-postform-parameters
http response 
POST /post?ids[a]=1234&ids[b]=hello HTTP/1.1
Content-Type: application/x-www-form-urlencoded

names[first]=thinkerou&names[second]=tianou

func main() {
  router := gin.Default()

  router.POST("/post", func(c *gin.Context) {

    ids := c.QueryMap("ids")
    names := c.PostFormMap("names")

    fmt.Printf("ids: %v; names: %v", ids, names)
  })
  router.Run(":8080")
}

ids: map[b:hello a:1234]; names: map[second:tianou first:thinkerou]

Upload files

https://blastcoding.com/golang-gin-gonic-documentation/#upload-files

Single file

https://blastcoding.com/golang-gin-gonic-documentation/#single-file

References issue #774 and detail example code.

file.Filename SHOULD NOT be trusted. See Content-Disposition on MDN and #1693

The filename is always optional and must not be used blindly by the application: path information should be stripped, and conversion to the server file system rules should be done.

func main() {
  router := gin.Default()
  // Set a lower memory limit for multipart forms (default is 32 MiB)
  router.MaxMultipartMemory = 8 << 20  // 8 MiB
  router.POST("/upload", func(c *gin.Context) {
    // Single file
    file, _ := c.FormFile("file")
    log.Println(file.Filename)

    // Upload the file to specific dst.
    c.SaveUploadedFile(file, dst)

    c.String(http.StatusOK, fmt.Sprintf("'%s' uploaded!", file.Filename))
  })
  router.Run(":8080")
}

How to curl:

CURL 
curl -X POST http://localhost:8080/upload \
  -F "file=@/Users/appleboy/test.zip" \
  -H "Content-Type: multipart/form-data"

Multiple files

https://blastcoding.com/golang-gin-gonic-documentation/#multiple-files

See the detail example code.

func main() {
  router := gin.Default()
  // Set a lower memory limit for multipart forms (default is 32 MiB)
  router.MaxMultipartMemory = 8 << 20  // 8 MiB
  router.POST("/upload", func(c *gin.Context) {
    // Multipart form
    form, _ := c.MultipartForm()
    files := form.File["upload[]"]

    for _, file := range files {
      log.Println(file.Filename)

      // Upload the file to specific dst.
      c.SaveUploadedFile(file, dst)
    }
    c.String(http.StatusOK, fmt.Sprintf("%d files uploaded!", len(files)))
  })
  router.Run(":8080")
}

How to curl:

CURL 
curl -X POST http://localhost:8080/upload \
  -F "upload[]=@/Users/appleboy/test1.zip" \
  -F "upload[]=@/Users/appleboy/test2.zip" \
  -H "Content-Type: multipart/form-data"

Grouping routes

https://blastcoding.com/golang-gin-gonic-documentation/#grouping-routes 
func main() {
  router := gin.Default()

  // Simple group: v1
  v1 := router.Group("/v1")
  {
    v1.POST("/login", loginEndpoint)
    v1.POST("/submit", submitEndpoint)
    v1.POST("/read", readEndpoint)
  }

  // Simple group: v2
  v2 := router.Group("/v2")
  {
    v2.POST("/login", loginEndpoint)
    v2.POST("/submit", submitEndpoint)
    v2.POST("/read", readEndpoint)
  }

  router.Run(":8080")
}

Blank Gin without middleware by default

https://blastcoding.com/golang-gin-gonic-documentation/#blank-gin-without-middleware-by-default

Use

r := gin.New()

instead of

// Default With the Logger and Recovery middleware already attached
r := gin.Default()

Using middleware

https://blastcoding.com/golang-gin-gonic-documentation/#using-middleware 
func main() {
  // Creates a router without any middleware by default
  r := gin.New()

  // Global middleware
  // Logger middleware will write the logs to gin.DefaultWriter even if you set with GIN_MODE=release.
  // By default gin.DefaultWriter = os.Stdout
  r.Use(gin.Logger())

  // Recovery middleware recovers from any panics and writes a 500 if there was one.
  r.Use(gin.Recovery())

  // Per route middleware, you can add as many as you desire.
  r.GET("/benchmark", MyBenchLogger(), benchEndpoint)

  // Authorization group
  // authorized := r.Group("/", AuthRequired())
  // exactly the same as:
  authorized := r.Group("/")
  // per group middleware! in this case we use the custom created
  // AuthRequired() middleware just in the "authorized" group.
  authorized.Use(AuthRequired())
  {
    authorized.POST("/login", loginEndpoint)
    authorized.POST("/submit", submitEndpoint)
    authorized.POST("/read", readEndpoint)

    // nested group
    testing := authorized.Group("testing")
    // visit 0.0.0.0:8080/testing/analytics
    testing.GET("/analytics", analyticsEndpoint)
  }

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

Custom Recovery behavior

https://blastcoding.com/golang-gin-gonic-documentation/#custom-recovery-behavior 
func main() {
  // Creates a router without any middleware by default
  r := gin.New()

  // Global middleware
  // Logger middleware will write the logs to gin.DefaultWriter even if you set with GIN_MODE=release.
  // By default gin.DefaultWriter = os.Stdout
  r.Use(gin.Logger())

  // Recovery middleware recovers from any panics and writes a 500 if there was one.
  r.Use(gin.CustomRecovery(func(c *gin.Context, recovered any) {
    if err, ok := recovered.(string); ok {
      c.String(http.StatusInternalServerError, fmt.Sprintf("error: %s", err))
    }
    c.AbortWithStatus(http.StatusInternalServerError)
  }))

  r.GET("/panic", func(c *gin.Context) {
    // panic with a string -- the custom middleware could save this to a database or report it to the user
    panic("foo")
  })

  r.GET("/", func(c *gin.Context) {
    c.String(http.StatusOK, "ohai")
  })

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

How to write log file

https://blastcoding.com/golang-gin-gonic-documentation/#how-to-write-log-file 
func main() {
  // Disable Console Color, you don't need console color when writing the logs to file.
  gin.DisableConsoleColor()

  // Logging to a file.
  f, _ := os.Create("gin.log")
  gin.DefaultWriter = io.MultiWriter(f)

  // Use the following code if you need to write the logs to file and console at the same time.
  // gin.DefaultWriter = io.MultiWriter(f, os.Stdout)

  router := gin.Default()
  router.GET("/ping", func(c *gin.Context) {
      c.String(http.StatusOK, "pong")
  })

&nbsp; &nbsp;router.Run(":8080")
}

Custom Log Format

https://blastcoding.com/golang-gin-gonic-documentation/#custom-log-format 
func main() {
  router := gin.New()

  // LoggerWithFormatter middleware will write the logs to gin.DefaultWriter
  // By default gin.DefaultWriter = os.Stdout
  router.Use(gin.LoggerWithFormatter(func(param gin.LogFormatterParams) string {

    // your custom format
    return fmt.Sprintf("%s - [%s] \"%s %s %s %d %s \"%s\" %s\"\n",
        param.ClientIP,
        param.TimeStamp.Format(time.RFC1123),
        param.Method,
        param.Path,
        param.Request.Proto,
        param.StatusCode,
        param.Latency,
        param.Request.UserAgent(),
        param.ErrorMessage,
    )
  }))
  router.Use(gin.Recovery())

  router.GET("/ping", func(c *gin.Context) {
    c.String(http.StatusOK, "pong")
  })

  router.Run(":8080")
}

Sample Output

::1 - [Fri, 07 Dec 2018 17:04:38 JST] "GET /ping HTTP/1.1 200 122.767µs "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.80 Safari/537.36" "

Controlling Log output coloring

https://blastcoding.com/golang-gin-gonic-documentation/#controlling-log-output-coloring

By default, logs output on console should be colorized depending on the detected TTY.

Never colorize logs:

func main() {
  // Disable log's color
  gin.DisableConsoleColor()

  // Creates a gin router with default middleware:
  // logger and recovery (crash-free) middleware
  router := gin.Default()

  router.GET("/ping", func(c *gin.Context) {
      c.String(http.StatusOK, "pong")
  })

  router.Run(":8080")
}

Always colorize logs:

func main() {
  // Force log's color
  gin.ForceConsoleColor()

  // Creates a gin router with default middleware:
  // logger and recovery (crash-free) middleware
  router := gin.Default()

  router.GET("/ping", func(c *gin.Context) {
      c.String(http.StatusOK, "pong")
  })

  router.Run(":8080")
}

Model binding and validation

https://blastcoding.com/golang-gin-gonic-documentation/#model-binding-and-validation

To bind a request body into a type, use model binding. We currently support binding of JSON, XML, YAML, TOML and standard form values (foo=bar&boo=baz).

Gin uses go-playground/validator/v10 for validation. Check the full docs on tags usage here.

Note that you need to set the corresponding binding tag on all fields you want to bind. For example, when binding from JSON, set json:"fieldname".

Also, Gin provides two sets of methods for binding:

  • Type – Must bind
  • Methods – Bind, BindJSON, BindXML, BindQuery, BindYAML, BindHeader, BindTOML
  • Behavior – These methods use MustBindWith under the hood. If there is a binding error, the request is aborted with c.AbortWithError(400, err).SetType(ErrorTypeBind). This sets the response status code to 400 and the Content-Type header is set to text/plain; charset=utf-8. Note that if you try to set the response code after this, it will result in a warning [GIN-debug] [WARNING] Headers were already written. Wanted to override status code 400 with 422. If you wish to have greater control over the behavior, consider using the ShouldBind equivalent method.
  • Type – Should bind
  • Methods – ShouldBind, ShouldBindJSON, ShouldBindXML, ShouldBindQuery, ShouldBindYAML, ShouldBindHeader, ShouldBindTOML,
  • Behavior – These methods use ShouldBindWith under the hood. If there is a binding error, the error is returned and it is the developer’s responsibility to handle the request and error appropriately.

When using the Bind-method, Gin tries to infer the binder depending on the Content-Type header. If you are sure what you are binding, you can use MustBindWith or ShouldBindWith.

You can also specify that specific fields are required. If a field is decorated with binding:"required" and has an empty value when binding, an error will be returned.

// Binding from JSON
type Login struct {
  User     string `form:"user" json:"user" xml:"user"  binding:"required"`
  Password string `form:"password" json:"password" xml:"password" binding:"required"`
}

func main() {
  router := gin.Default()

  // Example for binding JSON ({"user": "manu", "password": "123"})
  router.POST("/loginJSON", func(c *gin.Context) {
    var json Login
    if err := c.ShouldBindJSON(&json); err != nil {
      c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
      return
    }

    if json.User != "manu" || json.Password != "123" {
      c.JSON(http.StatusUnauthorized, gin.H{"status": "unauthorized"})
      return
    }

    c.JSON(http.StatusOK, gin.H{"status": "you are logged in"})
  })

  // Example for binding XML (
  //  <?xml version="1.0" encoding="UTF-8"?>
  //  <root>
  //    <user>manu</user>
  //    <password>123</password>
  //  </root>)
  router.POST("/loginXML", func(c *gin.Context) {
    var xml Login
    if err := c.ShouldBindXML(&xml); err != nil {
      c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
      return
    }

    if xml.User != "manu" || xml.Password != "123" {
      c.JSON(http.StatusUnauthorized, gin.H{"status": "unauthorized"})
      return
    }

    c.JSON(http.StatusOK, gin.H{"status": "you are logged in"})
  })

  // Example for binding a HTML form (user=manu&password=123)
  router.POST("/loginForm", func(c *gin.Context) {
    var form Login
    // This will infer what binder to use depending on the content-type header.
    if err := c.ShouldBind(&form); err != nil {
      c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
      return
    }

    if form.User != "manu" || form.Password != "123" {
      c.JSON(http.StatusUnauthorized, gin.H{"status": "unauthorized"})
      return
    }

    c.JSON(http.StatusOK, gin.H{"status": "you are logged in"})
  })

  // Listen and serve on 0.0.0.0:8080
  router.Run(":8080")
}

Sample request

CURL (this curl code is being applied in terminal) 
$ curl -v -X POST \
  http://localhost:8080/loginJSON \
  -H 'content-type: application/json' \
  -d '{ "user": "manu" }'
> POST /loginJSON HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.51.0
> Accept: */*
> content-type: application/json
> Content-Length: 18
>
* upload completely sent off: 18 out of 18 bytes
< HTTP/1.1 400 Bad Request
< Content-Type: application/json; charset=utf-8
< Date: Fri, 04 Aug 2017 03:51:31 GMT
< Content-Length: 100
<
{"error":"Key: 'Login.Password' Error:Field validation for 'Password' failed on the 'required' tag"}

Skip validate: when running the above example using the above the curl command, it returns error. Because the example use binding:"required" for Password. If use binding:"-" for Password, then it will not return error when running the above example again.

Custom Validators

https://blastcoding.com/golang-gin-gonic-documentation/#custom-validators

It is also possible to register custom validators. See the example code.

package main

import (
  "net/http"
  "time"

  "github.com/gin-gonic/gin"
  "github.com/gin-gonic/gin/binding"
  "github.com/go-playground/validator/v10"
)

// Booking contains binded and validated data.
type Booking struct {
  CheckIn  time.Time `form:"check_in" binding:"required,bookabledate" time_format:"2006-01-02"`
  CheckOut time.Time `form:"check_out" binding:"required,gtfield=CheckIn" time_format:"2006-01-02"`
}

var bookableDate validator.Func = func(fl validator.FieldLevel) bool {
  date, ok := fl.Field().Interface().(time.Time)
  if ok {
    today := time.Now()
    if today.After(date) {
      return false
    }
  }
  return true
}

func main() {
  route := gin.Default()

  if v, ok := binding.Validator.Engine().(*validator.Validate); ok {
    v.RegisterValidation("bookabledate", bookableDate)
  }

  route.GET("/bookable", getBookable)
  route.Run(":8085")
}

func getBookable(c *gin.Context) {
  var b Booking
  if err := c.ShouldBindWith(&b, binding.Query); err == nil {
    c.JSON(http.StatusOK, gin.H{"message": "Booking dates are valid!"})
  } else {
    c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
  }
}

$ curl "localhost:8085/bookable?check_in=2030-04-16&check_out=2030-04-17"
{"message":"Booking dates are valid!"}
$ curl "localhost:8085/bookable?check_in=2030-03-10&check_out=2030-03-09"
{"error":"Key: 'Booking.CheckOut' Error:Field validation for 'CheckOut' failed on the 'gtfield' tag"}

$ curl "localhost:8085/bookable?check_in=2000-03-09&check_out=2000-03-10"
{"error":"Key: 'Booking.CheckIn' Error:Field validation for 'CheckIn' failed on the 'bookabledate' tag"}%

Struct level validations can also be registered this way.
See the struct-lvl-validation example to learn more.

Only Bind Query String

https://blastcoding.com/golang-gin-gonic-documentation/#only-bind-query-string

ShouldBindQuery function only binds the query params and not the post data. See the detail information.

package main

import (
  "log"
  "net/http"

  "github.com/gin-gonic/gin"
)

type Person struct {
  Name    string `form:"name"`
  Address string `form:"address"`
}

func main() {
  route := gin.Default()
  route.Any("/testing", startPage)
  route.Run(":8085")
}

func startPage(c *gin.Context) {
  var person Person
  if c.ShouldBindQuery(&person) == nil {
    log.Println("====== Only Bind By Query String ======")
    log.Println(person.Name)
    log.Println(person.Address)
  }
  c.String(http.StatusOK, "Success")
}

Bind Query String or Post Data

https://blastcoding.com/golang-gin-gonic-documentation/#bind-query-string-or-post-data

See the detail information.

package main

import (
  "log"
  "net/http"
  "time"

  "github.com/gin-gonic/gin"
)

type Person struct {
  Name       string    `form:"name"`
  Address    string    `form:"address"`
  Birthday   time.Time `form:"birthday" time_format:"2006-01-02" time_utc:"1"`
  CreateTime time.Time `form:"createTime" time_format:"unixNano"`
  UnixTime   time.Time `form:"unixTime" time_format:"unix"`
}

func main() {
  route := gin.Default()
  route.GET("/testing", startPage)
  route.Run(":8085")
}

func startPage(c *gin.Context) {
  var person Person
  // If `GET`, only `Form` binding engine (`query`) used.
  // If `POST`, first checks the `content-type` for `JSON` or `XML`, then uses `Form` (`form-data`).
  // See more at https://github.com/gin-gonic/gin/blob/master/binding/binding.go#L88
  if c.ShouldBind(&person) == nil {
    log.Println(person.Name)
    log.Println(person.Address)
    log.Println(person.Birthday)
    log.Println(person.CreateTime)
    log.Println(person.UnixTime)
  }

  c.String(http.StatusOK, "Success")
}

Test it with:

curl -X GET "localhost:8085/testing?name=appleboy&address=xyz&birthday=1992-03-15&createTime=1562400033000000123&unixTime=1562400033"

Bind Uri

https://blastcoding.com/golang-gin-gonic-documentation/#bind-uri

See the detail information.

package main

import (
  "net/http"

  "github.com/gin-gonic/gin"
)

type Person struct {
  ID string `uri:"id" binding:"required,uuid"`
  Name string `uri:"name" binding:"required"`
}

func main() {
  route := gin.Default()
  route.GET("/:name/:id", func(c *gin.Context) {
    var person Person
    if err := c.ShouldBindUri(&person); err != nil {
      c.JSON(http.StatusBadRequest, gin.H{"msg": err.Error()})
      return
    }
    c.JSON(http.StatusOK, gin.H{"name": person.Name, "uuid": person.ID})
  })
  route.Run(":8088")
}

Test it with:

curl -v localhost:8088/thinkerou/987fbc97-4bed-5078-9f07-9141ba07c9f3
curl -v localhost:8088/thinkerou/not-uuid

Bind Header

https://blastcoding.com/golang-gin-gonic-documentation/#bind-header 
package main

import (
  "fmt"
  "net/http"

  "github.com/gin-gonic/gin"
)

type testHeader struct {
  Rate   int    `header:"Rate"`
  Domain string `header:"Domain"`
}

func main() {
  r := gin.Default()
  r.GET("/", func(c *gin.Context) {
    h := testHeader{}

    if err := c.ShouldBindHeader(&h); err != nil {
      c.JSON(http.StatusOK, err)
    }

    fmt.Printf("%#v\n", h)
    c.JSON(http.StatusOK, gin.H{"Rate": h.Rate, "Domain": h.Domain})
  })

  r.Run()

// client
// curl -H "rate:300" -H "domain:music" 127.0.0.1:8080/
// output
// {"Domain":"music","Rate":300}
}

Bind HTML checkboxes

https://blastcoding.com/golang-gin-gonic-documentation/#bind-html-checkboxes

See the detail information

main.go

main.go 
...

type myForm struct {
    Colors []string `form:"colors[]"`
}

...

func formHandler(c *gin.Context) {
    var fakeForm myForm
    c.ShouldBind(&fakeForm)
    c.JSON(http.StatusOK, gin.H{"color": fakeForm.Colors})
}

...

form.html

form.html 
<form action="/" method="POST">
    <p>Check some colors</p>
    <label for="red">Red</label>
    <input type="checkbox" name="colors[]" value="red" id="red">
    <label for="green">Green</label>
    <input type="checkbox" name="colors[]" value="green" id="green">
    <label for="blue">Blue</label>
    <input type="checkbox" name="colors[]" value="blue" id="blue">
    <input type="submit">
</form>

result:

{"color":["red","green","blue"]}

Multipart/Urlencoded binding

https://blastcoding.com/golang-gin-gonic-documentation/#multiparturlencoded-binding 
type ProfileForm struct {
  Name   string                `form:"name" binding:"required"`
  Avatar *multipart.FileHeader `form:"avatar" binding:"required"`

  // or for multiple files
  // Avatars []*multipart.FileHeader `form:"avatar" binding:"required"`
}

func main() {
  router := gin.Default()
  router.POST("/profile", func(c *gin.Context) {
    // you can bind multipart form with explicit binding declaration:
    // c.ShouldBindWith(&form, binding.Form)
    // or you can simply use autobinding with ShouldBind method:
    var form ProfileForm
    // in this case proper binding will be automatically selected
    if err := c.ShouldBind(&form); err != nil {
      c.String(http.StatusBadRequest, "bad request")
      return
    }

    err := c.SaveUploadedFile(form.Avatar, form.Avatar.Filename)
    if err != nil {
      c.String(http.StatusInternalServerError, "unknown error")
      return
    }

    // db.Save(&form)

    c.String(http.StatusOK, "ok")
  })
  router.Run(":8080")
}

Test it with:

CURL 
curl -X POST -v --form name=user --form "avatar=@./avatar.png" http://localhost:8080/profile

XML, JSON, YAML, TOML and ProtoBuf rendering

https://blastcoding.com/golang-gin-gonic-documentation/#xml-json-yaml-toml-and-protobuf-rendering 
func main() {
  r := gin.Default()

  // gin.H is a shortcut for map[string]any
  r.GET("/someJSON", func(c *gin.Context) {
    c.JSON(http.StatusOK, gin.H{"message": "hey", "status": http.StatusOK})
  })

  r.GET("/moreJSON", func(c *gin.Context) {
    // You also can use a struct
    var msg struct {
      Name    string `json:"user"`
      Message string
      Number  int
    }
    msg.Name = "Lena"
    msg.Message = "hey"
    msg.Number = 123
    // Note that msg.Name becomes "user" in the JSON
    // Will output  :   {"user": "Lena", "Message": "hey", "Number": 123}
    c.JSON(http.StatusOK, msg)
  })

  r.GET("/someXML", func(c *gin.Context) {
    c.XML(http.StatusOK, gin.H{"message": "hey", "status": http.StatusOK})
  })

  r.GET("/someYAML", func(c *gin.Context) {
    c.YAML(http.StatusOK, gin.H{"message": "hey", "status": http.StatusOK})
  })

  r.GET("/someTOML", func(c *gin.Context) {
    c.TOML(http.StatusOK, gin.H{"message": "hey", "status": http.StatusOK})
  })

  r.GET("/someProtoBuf", func(c *gin.Context) {
    reps := []int64{int64(1), int64(2)}
    label := "test"
    // The specific definition of protobuf is written in the testdata/protoexample file.
    data := &protoexample.Test{
      Label: &label,
      Reps:  reps,
    }
    // Note that data becomes binary data in the response
    // Will output protoexample.Test protobuf serialized data
    c.ProtoBuf(http.StatusOK, data)
  })

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

SecureJSON

https://blastcoding.com/golang-gin-gonic-documentation/#securejson

Using SecureJSON to prevent json hijacking. Default prepends "while(1)," to response body if the given struct is array values.

func main() {
  r := gin.Default()

  // You can also use your own secure json prefix
  // r.SecureJsonPrefix(")]}',\n")

  r.GET("/someJSON", func(c *gin.Context) {
    names := []string{"lena", "austin", "foo"}

    // Will output  :   while(1);["lena","austin","foo"]
    c.SecureJSON(http.StatusOK, names)
  })

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

JSONP

https://blastcoding.com/golang-gin-gonic-documentation/#jsonp

Using JSONP to request data from a server in a different domain. Add callback to response body if the query parameter callback exists.

func main() {
  r := gin.Default()

  r.GET("/JSONP", func(c *gin.Context) {
    data := gin.H{
      "foo": "bar",
    }

    //callback is x
    // Will output  :   x({\"foo\":\"bar\"})
    c.JSONP(http.StatusOK, data)
  })

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")

        // client
        // curl http://127.0.0.1:8080/JSONP?callback=x
}

AsciiJSON

https://blastcoding.com/golang-gin-gonic-documentation/#asciijson

Using AsciiJSON to Generates ASCII-only JSON with escaped non-ASCII characters.

func main() {
  r := gin.Default()

  r.GET("/someJSON", func(c *gin.Context) {
    data := gin.H{
      "lang": "GO语言",
      "tag":  "<br>",
    }

    // will output : {"lang":"GO\u8bed\u8a00","tag":"\u003cbr\u003e"}
    c.AsciiJSON(http.StatusOK, data)
  })

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

PureJSON

https://blastcoding.com/golang-gin-gonic-documentation/#purejson

Normally, JSON replaces special HTML characters with their unicode entities, e.g. < becomes \u003c. If you want to encode such characters literally, you can use PureJSON instead.
This feature is unavailable in Go 1.6 and lower.

func main() {
  r := gin.Default()

  // Serves unicode entities
  r.GET("/json", func(c *gin.Context) {
    c.JSON(http.StatusOK, gin.H{
      "html": "<b>Hello, world!</b>",
    })
  })

  // Serves literal characters
  r.GET("/purejson", func(c *gin.Context) {
    c.PureJSON(http.StatusOK, gin.H{
      "html": "<b>Hello, world!</b>",
    })
  })

  // listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

Serving static files

https://blastcoding.com/golang-gin-gonic-documentation/#serving-static-files 
func main() {
  router := gin.Default()
  router.Static("/assets", "./assets")
  router.StaticFS("/more_static", http.Dir("my_file_system"))
  router.StaticFile("/favicon.ico", "./resources/favicon.ico")
  router.StaticFileFS("/more_favicon.ico", "more_favicon.ico", http.Dir("my_file_system"))

  // Listen and serve on 0.0.0.0:8080
  router.Run(":8080")
}

Serving data from file

https://blastcoding.com/golang-gin-gonic-documentation/#serving-data-from-file 
func main() {
  router := gin.Default()

  router.GET("/local/file", func(c *gin.Context) {
    c.File("local/file.go")
  })

  var fs http.FileSystem = // ...
  router.GET("/fs/file", func(c *gin.Context) {
    c.FileFromFS("fs/file.go", fs)
  })
}

Serving data from reader

https://blastcoding.com/golang-gin-gonic-documentation/#serving-data-from-reader 
func main() {
  router := gin.Default()
  router.GET("/someDataFromReader", func(c *gin.Context) {
    response, err := http.Get("https://raw.githubusercontent.com/gin-gonic/logo/master/color.png")
    if err != nil || response.StatusCode != http.StatusOK {
      c.Status(http.StatusServiceUnavailable)
      return
    }

    reader := response.Body
     defer reader.Close()
    contentLength := response.ContentLength
    contentType := response.Header.Get("Content-Type")

    extraHeaders := map[string]string{
      "Content-Disposition": `attachment; filename="gopher.png"`,
    }

    c.DataFromReader(http.StatusOK, contentLength, contentType, reader, extraHeaders)
  })
  router.Run(":8080")
}

HTML rendering

https://blastcoding.com/golang-gin-gonic-documentation/#html-rendering

Using LoadHTMLGlob() or LoadHTMLFiles()

func main() {
  router := gin.Default()
  router.LoadHTMLGlob("templates/*")
  //router.LoadHTMLFiles("templates/template1.html", "templates/template2.html")
  router.GET("/index", func(c *gin.Context) {
    c.HTML(http.StatusOK, "index.tmpl", gin.H{
      "title": "Main website",
    })
  })
  router.Run(":8080")
}

templates/index.tmpl

templates/index.tmpl[GIN TEMPLATE FILE] 
<html>
  <h1>
    {{ .title }}
  </h1>
</html>

Using templates with same name in different directories

func main() {
  router := gin.Default()
  router.LoadHTMLGlob("templates/**/*")
  router.GET("/posts/index", func(c *gin.Context) {
    c.HTML(http.StatusOK, "posts/index.tmpl", gin.H{
      "title": "Posts",
    })
  })
  router.GET("/users/index", func(c *gin.Context) {
    c.HTML(http.StatusOK, "users/index.tmpl", gin.H{
      "title": "Users",
    })
  })
  router.Run(":8080")
}

templates/posts/index.tmpl

templates/posts/index.tmpl[GIN TEMPLATE FILE] 
{{ define "posts/index.tmpl" }}
<html><h1>
  {{ .title }}
</h1>
<p>Using posts/index.tmpl</p>
</html>
{{ end }}

templates/users/index.tmpl

templates/users/index.tmpl[GIN TEMPLATE FILE] 
{{ define "users/index.tmpl" }}
<html><h1>
  {{ .title }}
</h1>
<p>Using users/index.tmpl</p>
</html>
{{ end }}

Custom Template renderer

https://blastcoding.com/golang-gin-gonic-documentation/#custom-template-renderer

You can also use your own html template render

import "html/template"

func main() {
  router := gin.Default()
  html := template.Must(template.ParseFiles("file1", "file2"))
  router.SetHTMLTemplate(html)
  router.Run(":8080")
}

Custom Delimiters

You may use custom delims

  r := gin.Default()
  r.Delims("{[{", "}]}")
  r.LoadHTMLGlob("/path/to/templates")

Custom Template Funcs

See the detail example code.

main.go

main.go 
import (
  "fmt"
  "html/template"
  "net/http"
  "time"

  "github.com/gin-gonic/gin"
)

func formatAsDate(t time.Time) string {
  year, month, day := t.Date()
  return fmt.Sprintf("%d/%02d/%02d", year, month, day)
}

func main() {
  router := gin.Default()
  router.Delims("{[{", "}]}")
  router.SetFuncMap(template.FuncMap{
      "formatAsDate": formatAsDate,
  })
  router.LoadHTMLFiles("./testdata/template/raw.tmpl")

  router.GET("/raw", func(c *gin.Context) {
      c.HTML(http.StatusOK, "raw.tmpl", gin.H{
          "now": time.Date(2017, 07, 01, 0, 0, 0, 0, time.UTC),
      })
  })

  router.Run(":8080")
}

raw.tmpl

Date: {[{.now | formatAsDate}]}

Result:

Date: 2017/07/01

Multitemplate

https://blastcoding.com/golang-gin-gonic-documentation/#multitemplate

Gin allow by default use only one html.Template. Check a multitemplate render for using features like go 1.6 block template.

Redirects

https://blastcoding.com/golang-gin-gonic-documentation/#redirects

Issuing a HTTP redirect is easy. Both internal and external locations are supported.

r.GET("/test", func(c *gin.Context) {
  c.Redirect(http.StatusMovedPermanently, "http://www.google.com/")
})

Issuing a HTTP redirect from POST. Refer to issue: #444

r.POST("/test", func(c *gin.Context) {
  c.Redirect(http.StatusFound, "/foo")
})

Issuing a Router redirect, use HandleContext like below.

r.GET("/test", func(c *gin.Context) {
    c.Request.URL.Path = "/test2"
    r.HandleContext(c)
})
r.GET("/test2", func(c *gin.Context) {
    c.JSON(http.StatusOK, gin.H{"hello": "world"})
})

Custom Middleware

https://blastcoding.com/golang-gin-gonic-documentation/#custom-middleware 
func Logger() gin.HandlerFunc {
  return func(c *gin.Context) {
    t := time.Now()

    // Set example variable
    c.Set("example", "12345")

    // before request

    c.Next()

    // after request
    latency := time.Since(t)
    log.Print(latency)

    // access the status we are sending
    status := c.Writer.Status()
    log.Println(status)
  }
}

func main() {
  r := gin.New()
  r.Use(Logger())

  r.GET("/test", func(c *gin.Context) {
    example := c.MustGet("example").(string)

    // it would print: "12345"
    log.Println(example)
  })

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

Using BasicAuth() middleware

https://blastcoding.com/golang-gin-gonic-documentation/#using-basicauth-middleware 
// simulate some private data
var secrets = gin.H{
  "foo":    gin.H{"email": "foo@bar.com", "phone": "123433"},
  "austin": gin.H{"email": "austin@example.com", "phone": "666"},
  "lena":   gin.H{"email": "lena@guapa.com", "phone": "523443"},
}

func main() {
  r := gin.Default()

  // Group using gin.BasicAuth() middleware
  // gin.Accounts is a shortcut for map[string]string
  authorized := r.Group("/admin", gin.BasicAuth(gin.Accounts{
    "foo":    "bar",
    "austin": "1234",
    "lena":   "hello2",
    "manu":   "4321",
  }))

  // /admin/secrets endpoint
  // hit "localhost:8080/admin/secrets
  authorized.GET("/secrets", func(c *gin.Context) {
    // get user, it was set by the BasicAuth middleware
    user := c.MustGet(gin.AuthUserKey).(string)
    if secret, ok := secrets[user]; ok {
      c.JSON(http.StatusOK, gin.H{"user": user, "secret": secret})
    } else {
      c.JSON(http.StatusOK, gin.H{"user": user, "secret": "NO SECRET :("})
    }
  })

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

Goroutines inside a middleware

https://blastcoding.com/golang-gin-gonic-documentation/#goroutines-inside-a-middleware

When starting new Goroutines inside a middleware or handler, you SHOULD NOT use the original context inside it, you have to use a read-only copy.

func main() {
  r := gin.Default()

  r.GET("/long_async", func(c *gin.Context) {
    // create copy to be used inside the goroutine
    cCp := c.Copy()
    go func() {
      // simulate a long task with time.Sleep(). 5 seconds
      time.Sleep(5 * time.Second)

      // note that you are using the copied context "cCp", IMPORTANT
      log.Println("Done! in path " + cCp.Request.URL.Path)
    }()
  })

  r.GET("/long_sync", func(c *gin.Context) {
    // simulate a long task with time.Sleep(). 5 seconds
    time.Sleep(5 * time.Second)

    // since we are NOT using a goroutine, we do not have to copy the context
    log.Println("Done! in path " + c.Request.URL.Path)
  })

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

Custom HTTP configuration

https://blastcoding.com/golang-gin-gonic-documentation/#custom-http-configuration

Use http.ListenAndServe() directly, like this:

func main() {
  router := gin.Default()
  http.ListenAndServe(":8080", router)
}

or

func main() {
  router := gin.Default()

  s := &http.Server{
    Addr:           ":8080",
    Handler:        router,
    ReadTimeout:    10 * time.Second,
    WriteTimeout:   10 * time.Second,
    MaxHeaderBytes: 1 << 20,
  }
  s.ListenAndServe()
}

Support Let’s Encrypt

https://blastcoding.com/golang-gin-gonic-documentation/#support-lets-encrypt

example for 1-line LetsEncrypt HTTPS servers.

package main

import (
  "log"
  "net/http"

  "github.com/gin-gonic/autotls"
  "github.com/gin-gonic/gin"
)

func main() {
  r := gin.Default()

  // Ping handler
  r.GET("/ping", func(c *gin.Context) {
    c.String(http.StatusOK, "pong")
  })

  log.Fatal(autotls.Run(r, "example1.com", "example2.com"))
}

example for custom autocert manager.

package main

import (
  "log"
  "net/http"

  "github.com/gin-gonic/autotls"
  "github.com/gin-gonic/gin"
  "golang.org/x/crypto/acme/autocert"
)

func main() {
  r := gin.Default()

  // Ping handler
  r.GET("/ping", func(c *gin.Context) {
    c.String(http.StatusOK, "pong")
  })

  m := autocert.Manager{
    Prompt:     autocert.AcceptTOS,
    HostPolicy: autocert.HostWhitelist("example1.com", "example2.com"),
    Cache:      autocert.DirCache("/var/www/.cache"),
  }

  log.Fatal(autotls.RunWithManager(r, &m))
}

Run multiple service using Gin

https://blastcoding.com/golang-gin-gonic-documentation/#run-multiple-service-using-gin

See the question and try the following example:

package main

import (
  "log"
  "net/http"
  "time"

  "github.com/gin-gonic/gin"
  "golang.org/x/sync/errgroup"
)

var (
  g errgroup.Group
)

func router01() http.Handler {
  e := gin.New()
  e.Use(gin.Recovery())
  e.GET("/", func(c *gin.Context) {
    c.JSON(
      http.StatusOK,
      gin.H{
        "code":  http.StatusOK,
        "error": "Welcome server 01",
      },
    )
  })

  return e
}

func router02() http.Handler {
  e := gin.New()
  e.Use(gin.Recovery())
  e.GET("/", func(c *gin.Context) {
    c.JSON(
      http.StatusOK,
      gin.H{
        "code":  http.StatusOK,
        "error": "Welcome server 02",
      },
    )
  })

  return e
}

func main() {
  server01 := &http.Server{
    Addr:         ":8080",
    Handler:      router01(),
    ReadTimeout:  5 * time.Second,
    WriteTimeout: 10 * time.Second,
  }

  server02 := &http.Server{
    Addr:         ":8081",
    Handler:      router02(),
    ReadTimeout:  5 * time.Second,
    WriteTimeout: 10 * time.Second,
  }

  g.Go(func() error {
    err := server01.ListenAndServe()
    if err != nil && err != http.ErrServerClosed {
      log.Fatal(err)
    }
    return err
  })

  g.Go(func() error {
    err := server02.ListenAndServe()
    if err != nil && err != http.ErrServerClosed {
      log.Fatal(err)
    }
    return err
  })

  if err := g.Wait(); err != nil {
    log.Fatal(err)
  }
}

Graceful shutdown or restart

https://blastcoding.com/golang-gin-gonic-documentation/#graceful-shutdown-or-restart

There are a few approaches you can use to perform a graceful shutdown or restart. You can make use of third-party packages specifically built for that, or you can manually do the same with the functions and methods from the built-in packages.

Third-party packages

https://blastcoding.com/golang-gin-gonic-documentation/#third-party-packages

We can use fvbock/endless to replace the default ListenAndServe. Refer to issue #296 for more details.

router := gin.Default()
router.GET("/", handler)
// [...]
endless.ListenAndServe(":4242", router)

Alternatives:

  • grace: Graceful restart & zero downtime deploy for Go servers.
  • graceful: Graceful is a Go package enabling graceful shutdown of an http.Handler server.
  • manners: A polite Go HTTP server that shuts down gracefully.

Manually

https://blastcoding.com/golang-gin-gonic-documentation/#manually

In case you are using Go 1.8 or a later version, you may not need to use those libraries. Consider using http.Server‘s built-in Shutdown() method for graceful shutdowns. The example below describes its usage, and we’ve got more examples using gin here.

// +build go1.8

package main

import (
  "context"
  "log"
  "net/http"
  "os"
  "os/signal"
  "syscall"
  "time"

  "github.com/gin-gonic/gin"
)

func main() {
  router := gin.Default()
  router.GET("/", func(c *gin.Context) {
    time.Sleep(5 * time.Second)
    c.String(http.StatusOK, "Welcome Gin Server")
  })

  srv := &http.Server{
    Addr:    ":8080",
    Handler: router,
  }

  // Initializing the server in a goroutine so that
  // it won't block the graceful shutdown handling below
  go func() {
    if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
      log.Printf("listen: %s\n", err)
    }
  }()

  // Wait for interrupt signal to gracefully shutdown the server with
  // a timeout of 5 seconds.
  quit := make(chan os.Signal)
  // kill (no param) default send syscall.SIGTERM
  // kill -2 is syscall.SIGINT
  // kill -9 is syscall.SIGKILL but can't be caught, so don't need to add it
  signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
  <-quit
  log.Println("Shutting down server...")

  // The context is used to inform the server it has 5 seconds to finish
  // the request it is currently handling
  ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
  defer cancel()

  if err := srv.Shutdown(ctx); err != nil {
    log.Fatal("Server forced to shutdown:", err)
  }

  log.Println("Server exiting")
}

Build a single binary with templates

https://blastcoding.com/golang-gin-gonic-documentation/#build-a-single-binary-with-templates

You can build a server into a single binary containing templates by using the embed package.

package main

import (
  "embed"
  "html/template"
  "net/http"

  "github.com/gin-gonic/gin"
)

//go:embed assets/* templates/*
var f embed.FS

func main() {
  router := gin.Default()
  templ := template.Must(template.New("").ParseFS(f, "templates/*.tmpl", "templates/foo/*.tmpl"))
  router.SetHTMLTemplate(templ)

  // example: /public/assets/images/example.png
  router.StaticFS("/public", http.FS(f))

  router.GET("/", func(c *gin.Context) {
    c.HTML(http.StatusOK, "index.tmpl", gin.H{
      "title": "Main website",
    })
  })

  router.GET("/foo", func(c *gin.Context) {
    c.HTML(http.StatusOK, "bar.tmpl", gin.H{
      "title": "Foo website",
    })
  })

  router.GET("favicon.ico", func(c *gin.Context) {
    file, _ := f.ReadFile("assets/favicon.ico")
    c.Data(
      http.StatusOK,
      "image/x-icon",
      file,
    )
  })

  router.Run(":8080")
}

See a complete example in the https://github.com/gin-gonic/examples/tree/master/assets-in-binary/example02 directory.

Bind form-data request with custom struct

https://blastcoding.com/golang-gin-gonic-documentation/#bind-form-data-request-with-custom-struct

The follow example using custom struct:

type StructA struct {
    FieldA string `form:"field_a"`
}

type StructB struct {
    NestedStruct StructA
    FieldB string `form:"field_b"`
}

type StructC struct {
    NestedStructPointer *StructA
    FieldC string `form:"field_c"`
}

type StructD struct {
    NestedAnonyStruct struct {
        FieldX string `form:"field_x"`
    }
    FieldD string `form:"field_d"`
}

func GetDataB(c *gin.Context) {
    var b StructB
    c.Bind(&b)
    c.JSON(http.StatusOK, gin.H{
        "a": b.NestedStruct,
        "b": b.FieldB,
    })
}

func GetDataC(c *gin.Context) {
    var b StructC
    c.Bind(&b)
    c.JSON(http.StatusOK, gin.H{
        "a": b.NestedStructPointer,
        "c": b.FieldC,
    })
}

func GetDataD(c *gin.Context) {
    var b StructD
    c.Bind(&b)
    c.JSON(http.StatusOK, gin.H{
        "x": b.NestedAnonyStruct,
        "d": b.FieldD,
    })
}

func main() {
    r := gin.Default()
    r.GET("/getb", GetDataB)
    r.GET("/getc", GetDataC)
    r.GET("/getd", GetDataD)

    r.Run()
}

Using the command curl command result:

$ curl "http://localhost:8080/getb?field_a=hello&field_b=world"
{"a":{"FieldA":"hello"},"b":"world"}

$ curl "http://localhost:8080/getc?field_a=hello&field_c=world"
{"a":{"FieldA":"hello"},"c":"world"}

$ curl "http://localhost:8080/getd?field_x=hello&field_d=world"
{"d":"world","x":{"FieldX":"hello"}}

Try to bind body into different structs

https://blastcoding.com/golang-gin-gonic-documentation/#try-to-bind-body-into-different-structs

The normal methods for binding request body consumes c.Request.Body and they
cannot be called multiple times.

type formA struct {
  Foo string `json:"foo" xml:"foo" binding:"required"`
}

type formB struct {
  Bar string `json:"bar" xml:"bar" binding:"required"`
}

func SomeHandler(c *gin.Context) {
  objA := formA{}
  objB := formB{}
  // This c.ShouldBind consumes c.Request.Body and it cannot be reused.
  if errA := c.ShouldBind(&objA); errA == nil {
    c.String(http.StatusOK, `the body should be formA`)
  // Always an error is occurred by this because c.Request.Body is EOF now.
  } else if errB := c.ShouldBind(&objB); errB == nil {
    c.String(http.StatusOK, `the body should be formB`)
  } else {
    ...
  }
}

For this, you can use c.ShouldBindBodyWith.

func SomeHandler(c *gin.Context) {
  objA := formA{}
  objB := formB{}
  // This reads c.Request.Body and stores the result into the context.
  if errA := c.ShouldBindBodyWith(&objA, binding.Form); errA == nil {
    c.String(http.StatusOK, `the body should be formA`)
  // At this time, it reuses body stored in the context.
  } else if errB := c.ShouldBindBodyWith(&objB, binding.JSON); errB == nil {
    c.String(http.StatusOK, `the body should be formB JSON`)
  // And it can accepts other formats
  } else if errB2 := c.ShouldBindBodyWith(&objB, binding.XML); errB2 == nil {
    c.String(http.StatusOK, `the body should be formB XML`)
  } else {
    ...
  }
}
  1. c.ShouldBindBodyWith stores body into the context before binding. This has
    a slight impact to performance, so you should not use this method if you are
    enough to call binding at once.
  2. This feature is only needed for some formats — JSON, XML, MsgPack,
    ProtoBuf. For other formats, Query, Form, FormPost, FormMultipart,
    can be called by c.ShouldBind() multiple times without any damage to
    performance (See #1341).

Bind form-data request with custom struct and custom tag

https://blastcoding.com/golang-gin-gonic-documentation/#bind-form-data-request-with-custom-struct-and-custom-tag 
const (
  customerTag = "url"
  defaultMemory = 32 << 20
)

type customerBinding struct {}

func (customerBinding) Name() string {
  return "form"
}

func (customerBinding) Bind(req *http.Request, obj any) error {
  if err := req.ParseForm(); err != nil {
    return err
  }
  if err := req.ParseMultipartForm(defaultMemory); err != nil {
    if err != http.ErrNotMultipart {
      return err
    }
  }
  if err := binding.MapFormWithTag(obj, req.Form, customerTag); err != nil {
    return err
  }
  return validate(obj)
}

func validate(obj any) error {
  if binding.Validator == nil {
    return nil
  }
  return binding.Validator.ValidateStruct(obj)
}

// Now we can do this!!!
// FormA is an external type that we can't modify it's tag
type FormA struct {
  FieldA string `url:"field_a"`
}

func ListHandler(s *Service) func(ctx *gin.Context) {
  return func(ctx *gin.Context) {
    var urlBinding = customerBinding{}
    var opt FormA
    err := ctx.MustBindWith(&opt, urlBinding)
    if err != nil {
      ...
    }
    ...
  }
}

http2 server push

https://blastcoding.com/golang-gin-gonic-documentation/#http2-server-push

http.Pusher is supported only go1.8+. See the golang blog for detail information.

package main

import (
  "html/template"
  "log"
  "net/http"

  "github.com/gin-gonic/gin"
)

var html = template.Must(template.New("https").Parse(`
<html>
<head>
  <title>Https Test</title>
  <script src="/assets/app.js"></script>
</head>
<body>
  <h1 style="color:red;">Welcome, Ginner!</h1>
</body>
</html>
`))

func main() {
  r := gin.Default()
  r.Static("/assets", "./assets")
  r.SetHTMLTemplate(html)

  r.GET("/", func(c *gin.Context) {
    if pusher := c.Writer.Pusher(); pusher != nil {
      // use pusher.Push() to do server push
      if err := pusher.Push("/assets/app.js", nil); err != nil {
        log.Printf("Failed to push: %v", err)
      }
    }
    c.HTML(http.StatusOK, "https", gin.H{
      "status": "success",
    })
  })

  // Listen and Server in https://127.0.0.1:8080
  r.RunTLS(":8080", "./testdata/server.pem", "./testdata/server.key")
}

Define format for the log of routes

https://blastcoding.com/golang-gin-gonic-documentation/#define-format-for-the-log-of-routes

The default log of routes is:

[GIN-debug] POST   /foo                      --> main.main.func1 (3 handlers)
[GIN-debug] GET    /bar                      --> main.main.func2 (3 handlers)
[GIN-debug] GET    /status                   --> main.main.func3 (3 handlers)

If you want to log this information in given format (e.g. JSON, key values or something else), then you can define this format with gin.DebugPrintRouteFunc.
In the example below, we log all routes with standard log package but you can use another log tools that suits of your needs.

import (
  "log"
  "net/http"

  "github.com/gin-gonic/gin"
)

func main() {
  r := gin.Default()
  gin.DebugPrintRouteFunc = func(httpMethod, absolutePath, handlerName string, nuHandlers int) {
    log.Printf("endpoint %v %v %v %v\n", httpMethod, absolutePath, handlerName, nuHandlers)
  }

  r.POST("/foo", func(c *gin.Context) {
    c.JSON(http.StatusOK, "foo")
  })

  r.GET("/bar", func(c *gin.Context) {
    c.JSON(http.StatusOK, "bar")
  })

  r.GET("/status", func(c *gin.Context) {
    c.JSON(http.StatusOK, "ok")
  })

  // Listen and Server in http://0.0.0.0:8080
  r.Run()
}

Set and get a cookie

https://blastcoding.com/golang-gin-gonic-documentation/#set-and-get-a-cookie 
import (
  "fmt"

  "github.com/gin-gonic/gin"
)

func main() {
  router := gin.Default()

  router.GET("/cookie", func(c *gin.Context) {

      cookie, err := c.Cookie("gin_cookie")

      if err != nil {
          cookie = "NotSet"
          c.SetCookie("gin_cookie", "test", 3600, "/", "localhost", false, true)
      }

      fmt.Printf("Cookie value: %s \n", cookie)
  })

  router.Run()
}

Don’t trust all proxies

https://blastcoding.com/golang-gin-gonic-documentation/#dont-trust-all-proxies

Gin lets you specify which headers to hold the real client IP (if any),
as well as specifying which proxies (or direct clients) you trust to
specify one of these headers.

Use function SetTrustedProxies() on your gin.Engine to specify network addresses
or network CIDRs from where clients which their request headers related to client
IP can be trusted. They can be IPv4 addresses, IPv4 CIDRs, IPv6 addresses or
IPv6 CIDRs.

Attention: Gin trust all proxies by default if you don’t specify a trusted
proxy using the function above, this is NOT safe. At the same time, if you don’t
use any proxy, you can disable this feature by using Engine.SetTrustedProxies(nil),
then Context.ClientIP() will return the remote address directly to avoid some
unnecessary computation.

import (
  "fmt"

  "github.com/gin-gonic/gin"
)

func main() {
  router := gin.Default()
  router.SetTrustedProxies([]string{"192.168.1.2"})

  router.GET("/", func(c *gin.Context) {
    // If the client is 192.168.1.2, use the X-Forwarded-For
    // header to deduce the original client IP from the trust-
    // worthy parts of that header.
    // Otherwise, simply return the direct client IP
    fmt.Printf("ClientIP: %s\n", c.ClientIP())
  })
  router.Run()
}

Notice: If you are using a CDN service, you can set the Engine.TrustedPlatform
to skip TrustedProxies check, it has a higher priority than TrustedProxies.
Look at the example below:

import (
  "fmt"

  "github.com/gin-gonic/gin"
)

func main() {
  router := gin.Default()
  // Use predefined header gin.PlatformXXX
  router.TrustedPlatform = gin.PlatformGoogleAppEngine
  // Or set your own trusted request header for another trusted proxy service
  // Don't set it to any suspect request header, it's unsafe
  router.TrustedPlatform = "X-CDN-IP"

  router.GET("/", func(c *gin.Context) {
    // If you set TrustedPlatform, ClientIP() will resolve the
    // corresponding header and return IP directly
    fmt.Printf("ClientIP: %s\n", c.ClientIP())
  })
  router.Run()
}

Testing

https://blastcoding.com/golang-gin-gonic-documentation/#Testing

The net/http/httptest package is preferable way for HTTP testing.

package main

import (
  "net/http"

  "github.com/gin-gonic/gin"
)

func setupRouter() *gin.Engine {
  r := gin.Default()
  r.GET("/ping", func(c *gin.Context) {
    c.String(http.StatusOK, "pong")
  })
  return r
}

func main() {
  r := setupRouter()
  r.Run(":8080")00
}

Test for code example above:

package main

import (
  "net/http"
  "net/http/httptest"
  "testing"

  "github.com/stretchr/testify/assert"
)

func TestPingRoute(t *testing.T) {
  router := setupRouter()

  w := httptest.NewRecorder()
  req, _ := http.NewRequest(http.MethodGet, "/ping", nil)
  router.ServeHTTP(w, req)

  assert.Equal(t, http.StatusOK, w.Code)
  assert.Equal(t, "pong", w.Body.String())
}
Category: go
Something wrong? If you found an error or mistake in the content you can contact me on Twitter | @luisg2249_luis.
Post info
Author:Luis Gomez Created: 19th Jun 2023 Last Update: 6th Oct 2023
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