code: func (c *Client) PingAsync() FuturePingResult {
  	cmd := btcjson.NewPingCmd()
  	return c.sendCmd(cmd)
  }
docs: // PingAsync 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 Ping for the blocking version and more details.