code: func (sm *SyncManager) Pause() chan<- struct{} {
  	c := make(chan struct{})
  	sm.msgChan <- pauseMsg{c}
  	return c
  }
docs: // Pause pauses the sync manager until the returned channel is closed.
  //
  // Note that while paused, all peer and block processing is halted.  The
  // message sender should avoid pausing the sync manager for long durations.