type Clock interface {
	Now() time.Time
	Sleep(d time.Duration)
	Since(t time.Time) time.Duration
	// After waits for the duration to elapse and then sends the current time
	// on the returned channel.
	// It is equivalent to clock.NewTimer(d).C.
	// The underlying Timer is not recovered by the garbage collector
	// until the timer fires. If efficiency is a concern, use clock.NewTimer
	// instead and call Timer.Stop if the timer is no longer needed.
	After(d time.Duration) <-chan time.Time

	NewTimer(d time.Duration) Timer
	NewTicker(d time.Duration) Ticker
}

type Ticker interface {
	C() <-chan time.Time
	Stop()
}

type Timer interface {
	C() <-chan time.Time
	Reset(d time.Duration) bool
	Stop() bool
}