code: func (a *Agent) syncPausedCh() <-chan struct{} {
  	a.syncMu.Lock()
  	defer a.syncMu.Unlock()
  	return a.syncCh
  }
docs: // syncPausedCh returns either a channel or nil. If nil sync is not paused. If
  // non-nil, the channel will be closed when sync resumes.