Enable await for CancellationToken

CancellationTokenAsynchronousExtensions.cs

using System;
using System.Runtime.CompilerServices;
using System.Threading;

public static class CancellationTokenAsynchronousExtensions
{
    public static CancellationTokenAwaiter GetAwaiter(this CancellationToken cancellationToken)
    {
        return new CancellationTokenAwaiter(cancellationToken);
    }

    public struct CancellationTokenAwaiter : INotifyCompletion
    {
        private readonly CancellationToken cancellationToken;

        public CancellationTokenAwaiter(CancellationToken cancellationToken)
        {
            this.cancellationToken = cancellationToken;
        }

        public bool IsCompleted => cancellationToken.IsCancellationRequested;

        public void OnCompleted(Action continuation) => cancellationToken.Register(continuation);

        public void GetResult()
        {
            if (cancellationToken.IsCancellationRequested)
                return;

            using (var evt = new ManualResetEventSlim())
                evt.Wait(cancellationToken);
        }
    }
}