cs

namespace testchannels
{
    internal class Program
    {
        private static BlockingCollection<Action> _queue = new();
        private static CancellationTokenSource _currentCts;
        private static object _sync = new();

        static async Task Main(string[] args)
        {
            var queueProcessingTask = Task.Run(QueueProcessor);

            _queue.Add(
                () => SetStateOn(TimeSpan.FromSeconds(5),
                () => SetStateOff(TimeSpan.FromSeconds(3))));

            _queue.Add(() => Console.WriteLine("print last task"));

            var key = Console.ReadKey().Key;
            if (key == ConsoleKey.C)
            {
                Kill();
            }

            _queue.CompleteAdding();
            await queueProcessingTask;
        }

        private static void SetStateOn(TimeSpan delay, Action cancelledAction)
        {
            lock (_sync)
            {
                _currentCts = new CancellationTokenSource();
            }

            var token = _currentCts.Token;

            DoWork(token, delay, cancelledAction);
        }

        private static void SetStateOff(TimeSpan delay)
        {
            lock (_sync)
            {
                _currentCts = new CancellationTokenSource(delay);
            }

            var token = _currentCts.Token;

            DoAnotherWork(token);
        }

        private static void QueueProcessor()
        {
            foreach (var action in _queue.GetConsumingEnumerable())
            {
                action();
            }
        }

        private static void Kill()
        {
            //while (_queue.TryTake(out _)) { }

            lock (_sync)
            {
                _currentCts?.Cancel();
            }
        }

        private static void DoWork(
            CancellationToken ct, TimeSpan delay, Action cancelledAction)
        {
            DateTime endAt = DateTime.Now.Add(delay);
            while (DateTime.Now < endAt)
            {

                if (ct.IsCancellationRequested)
                {
                    cancelledAction.Invoke();
                    return;
                }

                Console.WriteLine("...");
            }
        }

        private static void DoAnotherWork(
            CancellationToken ct)
        {
            while (!ct.IsCancellationRequested)
            {
                Console.WriteLine("!!!");
            }
        }
    }
}