code: func (s *syncServer) notify(sn *SyncNote) {
  	s.sessionLock.RLock()
  	sessions := s.sessions
  	s.sessionLock.RUnlock()
  	for _, ss := range sessions {
  		ss.addNote(sn)
  	}
  }
docs: // notify queues a synchronisation notification with each of the active
  // synchronisation sessions.