code: func (n *Node) Attach() (*rpc.Client, error) {
  	n.lock.RLock()
  	defer n.lock.RUnlock()
  
  	if n.server == nil {
  		return nil, ErrNodeStopped
  	}
  	return rpc.DialInProc(n.inprocHandler), nil
  }
docs: // Attach creates an RPC client attached to an in-process API handler.