Automatically returns JSON when you don’t want to bother with every err!=nil, using Gin framework.


Copy the eh.go and preset.go file to wherever you want.

Define your Data Transfer Object with “eh” tags.

There are 3 meaningful tags, others stand for default values:

  1. eh:"err" – the field with err tag will be returned as a string, its value equals to err.Error()
  2. eh:"" – the field with empty tag will remain the default value of the type, you can also omit the tag
  3. eh:"pre:" – the field will be set the same as the variable in Preset struct with the same name, e.g. field with pre:CodeOK will be set with Preset.CodeOK (200, int64). Be aware of the spelling: p,r,e,colon. The type of the original field and the according ” Preset variable” must be the same, otherwise will cause a panic.


package main

import (
	eh "gin-error-handler"

type User struct {
	Name string `json:"name,omitempty"`

type UserLoginResp struct {
	Seq  int64  `json:"seq" eh:"-1"`                     // will be -1
	Code int64  `json:"code" eh:"pre:CodeUncaughtError"` // will be filled with Preset.CodeUncaughtError (551)
	Msg  string `json:"msg" eh:"err"`                    // will eventually be err.Error()
	User *User  `json:"user,omitempty" eh:""`            // will omit this field

func handler(c *gin.Context) {
	// create a new handler with *gin.Context and your JSON interface
	errHandler := eh.JSONHandler{
		C: c,
		V: UserLoginResp{},
	err := errors.New("something went wrong")              // some error occurred
	errHandler.Handle(err, http.StatusInternalServerError) // handle the error
	//errHandler.Handle(err) // will use http.StatusOK if you don't specify the code                // handle the error

func main() {
	req, _ := http.NewRequest(http.MethodGet, "/err", nil) // make a mock request
	rec := httptest.NewRecorder()                          // record the mock request
	// use Gin to handle the request
	r := gin.Default()
	r.GET("/err", handler)
	r.ServeHTTP(rec, req)


{"seq":-1,"code":551,"msg":"something went wrong"}


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