using System;

using System.Threading;

using System.Threading.Tasks;

​

​

public class Program

{

    public async static Task Main()

    {

        using CancellationTokenSource cts = new();

        await cts.CancelAsync();

​

        using SemaphoreSlim ss = new(initialCount: 1, maxCount: 1);

​

        try {

            await ss.WaitAsync(cts.Token);

        } finally {

            ss.Release();

        }

    }

}