marshal.go

package main

import (
	"encoding/json"
	"fmt"
	"time"
)

type MyUser struct {
	ID       int64     `json:"id"`
	Name     string    `json:"name"`
	LastSeen time.Time `json:"lastSeen"`
}

func (u *MyUser) MarshalJSON() ([]byte, error) {
	//return json.Marshal(
	//	&struct {
	//		ID       int64  `json:"id"`
	//		Name     string `json:"name"`
	//		LastSeen string `json:"lastSeen"`
	//	}{
	//		ID:       u.ID,
	//		Name:     u.Name,
	//		LastSeen: u.LastSeen.Format("2006-01-02 15:04:05"),
	//	})

	// return json.Marshal(
	// 	&struct {
	// 		*MyUser
	// 		LastSeen string `json:"lastSeen"`
	// 	}{
	// 		MyUser:   u,
	// 		LastSeen: u.LastSeen.Format("2006-01-02 15:04:05"),
	// 	},
	// )

	type Alias MyUser

	return json.Marshal(
		&struct {
			*Alias
			LastSeen string `json:"lastSeen"`
		}{
			Alias:    (*Alias)(u),
			LastSeen: u.LastSeen.Format("2006-01-02 15:04:05"),
		},
	)
}

type cUser MyUser

func main() {
	cUser := &cUser{123, "zhangwei", time.Now()}
	fmt.Println(cUser.ID)
	// u := &MyUser{1, "Ken", time.Now()}
	// bs, _ := json.Marshal(u)

	// os.Stdout.Write(bs)

	f := func(res string) {
		fmt.Println(res)
	}
	doAsync(f)
}

func doAsync(callback func(string)) {
	t := time.NewTimer(2 * time.Second)

	<-t.C
	callback("response")
}