Inheritance: IAsyncTimer
        public DelayedMessagePoller(string basePath, string delayedDir)
        {
            this.basePath = basePath;
            timer         = new AsyncTimer();

            delayedRootDirectory = delayedDir;
        }
 void StartHeartbeats()
 {
     Logger.Debug($"Start sending heartbeats every {heartbeatInterval}");
     heartbeatTimer = new AsyncTimer();
     heartbeatTimer.Start(SendHeartbeatMessage, heartbeatInterval, e => { });
 }