timekeeper

type TimeKeeper interface {
	// After waits for the duration to elapse and then sends the current
	// time on the returned channel.
	After(d time.Duration) <-chan time.Time
	// Sleep pauses the current goroutine for at least the duration d. A
	// negative or zero duration causes Sleep to return immediately.
	Sleep(d time.Duration)
	// Current time.
	Now() time.Time
}