sample using obj,MarshalJSON()

main.go

package main

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

type JSONTime struct {
	time.Time
}

func (t JSONTime) MarshalJSON() ([]byte, error) {
	formated := t.Format("2006/01/02 15:04")
	return json.Marshal(formated)
}

type Sample struct {
	DateTime JSONTime `json:"date_time,omitempty"`
	Name     string   `json:"name,omitempty"`
}

func main() {
	obj := Sample{
		DateTime: JSONTime{time.Now()},
		Name:     "NANA NUNU",
	}
	b, err := json.Marshal(obj)
	if err != nil {
		panic(err)
	}
	fmt.Println(string(b))
}