PingPongMonitor alive even after closing connection

[drauch]

In SlackConnection.Close the _pingPongMonitor is not stopped. Therefore the Timer in the ping-pong monitor keeps a reference and holds the connection alive (no GC) + it tries to ping-pong every 5 s although I closed the corresponding SlackConnection.

I suggest adding a method StopMonitor to IPingPongMonitor which disables the timer:

        public void StopMonitor()
        {
            _timer?.Dispose();
            _timer = null;
        }

Any objections?

Best regards,
D.R.

[drauch]

Note: we're using SlackConnector not in the "get notified for each message" way but in a "when we receive a webhook we open a connection, send a few messages, then close the connection" way. As all connections are kept alive by the ping-pong monitor we also face unnecessary resource consumption and in the end even port exhaustion.