code: func (n *Node) RemoteAPIAddr() (string, error) {
  	n.RLock()
  	defer n.RUnlock()
  	if n.manager == nil {
  		return "", errors.New("manager is not running")
  	}
  	addr := n.manager.Addr()
  	if addr == "" {
  		return "", errors.New("manager addr is not set")
  	}
  	return addr, nil
  }
docs: // RemoteAPIAddr returns address on which remote manager api listens.
  // Returns nil if node is not manager.