ItShouldCollectWatcher.cs

[TestFixture]
public class WatcherTests
{
    [Test]
    public async Task ItShouldCollectWatcher()
    {
        var _ = new Watcher();
        GC.Collect();
        GC.Collect();
        await Task.Delay(5000);
    }

    public class Watcher
    {
        private readonly CancellationTokenSource _tokenSource = new CancellationTokenSource();
        public Watcher()
        {
            Watch(_tokenSource.Token);
        }

        private async void Watch(CancellationToken cancellationToken)
        {
            while (!cancellationToken.IsCancellationRequested)
            {
                try
                {
                    await Task.Delay(1000, cancellationToken);
                    Console.WriteLine("I am still alive");
                }
                catch (OperationCanceledException)
                {
                }
            }
        }
        ~Watcher()
        {
            _tokenSource.Cancel();
        }
    }
}