golang_json_datetime.go

package main

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

type Duration time.Duration

func (d *Duration) UnmarshalJSON(b []byte) (err error) {
	if b[0] == '"' {
		sd := string(b[1 : len(b)-1])
		d.Duration, err = time.ParseDuration(sd)
		return
	}

	var id int64
	id, err = json.Number(string(b)).Int64()
	d.Duration = time.Duration(id)

	return
}

func (d Duration) MarshalJSON() (b []byte, err error) {
	return []byte(fmt.Sprintf(`"%s"`, d.String())), nil
}

type Astruct struct {
	Foo      string        `json:"baz"`
	Date     time.Time     `json:"date"`
	Dur Duration `json:duration`
}

func main() {
	fiveSec, _ := time.ParseDuration("5s")
	fmt.Println(fiveSec)

	a := Astruct{Foo: "bar", Date: time.Now(), Dur: fiveSec}
	fmt.Println(a)

	b, err := json.Marshal(a)
	if err != nil {
		fmt.Println("error: ", err)
	}
	fmt.Println(string(b))

}