code: func (sm *SyncManager) DonePeer(peer *peerpkg.Peer) {
  	// Ignore if we are shutting down.
  	if atomic.LoadInt32(&sm.shutdown) != 0 {
  		return
  	}
  
  	sm.msgChan <- &donePeerMsg{peer: peer}
  }
docs: // DonePeer informs the blockmanager that a peer has disconnected.