private void BTN_Exit_Click(object sender, EventArgs e)
        {
            WorkerBarber.CancelAsync();
            WorkerQueue.CancelAsync();

            BTN_Start.Enabled     = true;
            BTN_Exit.Enabled      = false;
            BTN_NewClient.Enabled = false;
        }
        private void WorkerQueue_DoWork(object sender, DoWorkEventArgs e)
        {
            queue();
            WorkerQueue.CancelAsync();

            if (WorkerQueue.CancellationPending == true)
            {
                e.Cancel = true;
                return;
            }
        }