clock for testing

clock.go

package clock

import (
	"flag"
	"time"
)

type NowFunc func() time.Time

var nowFunc NowFunc

func init() {
	ResetNowFunc()
}

func Now() time.Time {
	return nowFunc()
}

func ForceNow(t time.Time) {
	SetNowFunc(func() time.Time {
		return t
	})
}

func SetNowFunc(f NowFunc) {
	if flag.Lookup("test.v") == nil {
		panic("not testing!")
	}
	nowFunc = f
}

func ResetNowFunc() {
	nowFunc = time.Now
}