Cacher is the code snippet organizer for pro developers

    public static async Task<T> WithCancellation<T>(
        this Task<T> task, CancellationToken cancellationToken)
    {
        var tcs = new TaskCompletionSource<bool>();
        using(cancellationToken.Register(
                    s => ((TaskCompletionSource<bool>)s).TrySetResult(true), tcs))
            if (task != await Task.WhenAny(task, tcs.Task))
                throw new OperationCanceledException(cancellationToken);
        return await task;
    }