clock

type Clock interface {

	// Now returns the current clock time.
	Now() time.Time

	// After waits for the duration to elapse and then sends the
	// current time on the returned channel.
	After(time.Duration) <-chan time.Time

	// AfterFunc waits for the duration to elapse and then calls f in its own goroutine.
	// It returns a Timer that can be used to cancel the call using its Stop method.
	AfterFunc(time.Duration, func()) Timer
}

type Timer interface {

	// Reset changes the timer to expire after duration d.
	// It returns true if the timer had been active, false if
	// the timer had expired or been stopped.
	Reset(time.Duration) bool

	// Stop prevents the Timer from firing. It returns true if
	// the call stops the timer, false if the timer has already expired or been stopped.
	// Stop does not close the channel, to prevent a read
	// from the channel succeeding incorrectly.
	Stop() bool
}