code: func NodeID() []byte {
  	defer nodeMu.Unlock()
  	nodeMu.Lock()
  	if nodeID == zeroID {
  		setNodeInterface("")
  	}
  	nid := nodeID
  	return nid[:]
  }
docs: // NodeID returns a slice of a copy of the current Node ID, setting the Node ID
  // if not already set.