code: func (f *FakeClock) setTimeLocked(t time.Time) {
  	f.time = t
  	newWaiters := make([]fakeClockWaiter, 0, len(f.waiters))
  	for i := range f.waiters {
  		w := &f.waiters[i]
  		if !w.targetTime.After(t) {
  			w.destChan <- t
  		} else {
  			newWaiters = append(newWaiters, f.waiters[i])
  		}
  	}
  	f.waiters = newWaiters
  }
docs: // Actually changes the time and checks any waiters. f must be write-locked.