code: func (c *Client) NodeAsync(command btcjson.NodeSubCmd, host string,
  	connectSubCmd *string) FutureNodeResult {
  	cmd := btcjson.NewNodeCmd(command, host, connectSubCmd)
  	return c.sendCmd(cmd)
  }
docs: // NodeAsync returns an instance of a type that can be used to get the result
  // of the RPC at some future time by invoking the Receive function on the
  // returned instance.
  //
  // See Node for the blocking version and more details.