code: func newPeerConnection(id string, version int, peer Peer, logger log.Logger) *peerConnection {
  	return &peerConnection{
  		id:      id,
  		lacking: make(map[common.Hash]struct{}),
  
  		peer: peer,
  
  		version: version,
  		log:     logger,
  	}
  }
docs: // newPeerConnection creates a new downloader peer.