TaskCompletionSource и продолжения в том же потоке.¶

class Program
{
    private static ManualResetEventSlim _mutex = new ManualResetEventSlim();

    public static async Task Deadlock()
    {
        await ProcessAsync();
        _mutex.Wait();
    }

    private static Task ProcessAsync()
    {
        var tcs = new TaskCompletionSource<bool>();

        Task.Run(() =>
        {
            Thread.Sleep(2000); // Simulate some work
            tcs.SetResult(true);
            _mutex.Set();
        });

        return tcs.Task;
    }

    static void Main(string[] args)
    {
        Deadlock().Wait();
        Console.WriteLine("Will never get there");
    }
}