code: func (c *Client) NotifyNewTransactionsAsync(verbose bool) FutureNotifyNewTransactionsResult {
  	// Not supported in HTTP POST mode.
  	if c.config.HTTPPostMode {
  		return newFutureError(ErrWebsocketsRequired)
  	}
  
  	// Ignore the notification if the client is not interested in
  	// notifications.
  	if c.ntfnHandlers == nil {
  		return newNilFutureResult()
  	}
  
  	cmd := btcjson.NewNotifyNewTransactionsCmd(&verbose)
  	return c.sendCmd(cmd)
  }
docs: // NotifyNewTransactionsAsync 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 NotifyNewTransactionsAsync for the blocking version and more details.
  //
  // NOTE: This is a btcd extension and requires a websocket connection.