code: func (s *Snapshotter) updateClock() {
  	lastSeen := s.clock.Time() - 1
  	if lastSeen > s.lastClock {
  		s.lastClock = lastSeen
  		s.tryAppend(fmt.Sprintf("clock: %d\n", s.lastClock))
  	}
  }
docs: // updateClock is called periodically to check if we should udpate our
  // clock value. This is done after member events but should also be done
  // periodically due to race conditions with join and leave intents