clock

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

	// NewTicker returns a new Ticker.
	NewTicker(d time.Duration) Ticker

	// Now returns the current local time.
	Now() time.Time
}

type Ticker interface {
	// C returns the channel on which the ticks are delivered.
	C() <-chan time.Time

	// Stop the Ticker.
	Stop()
}