qdr.fnd/qdr.fnd.core/Thread/Extensions/TaskExt.cs

using System;
using System.Threading;
using System.Threading.Tasks;

namespace Quadarax.Foundation.Core.Thread.Extensions
{
    public static class TaskExt
    {
        public static async Task<TResult> TimeoutAfter<TResult>(this Task<TResult> task, TimeSpan timeout) {

            using (var timeoutCancellationTokenSource = new CancellationTokenSource()) {

                var completedTask = await Task.WhenAny(task, Task.Delay(timeout, timeoutCancellationTokenSource.Token));
                if (completedTask == task) {
                    timeoutCancellationTokenSource.Cancel();
                    return await task;  // Very important in order to propagate exceptions
                }

                throw new TimeoutException("The operation has timed out.");
            }
        }

        public static async Task TimeoutAfter(this Task task, TimeSpan timeout) {

            using (var timeoutCancellationTokenSource = new CancellationTokenSource()) {

                var completedTask = await Task.WhenAny(task, Task.Delay(timeout, timeoutCancellationTokenSource.Token));
                if (completedTask == task) {
                    timeoutCancellationTokenSource.Cancel();
                    await task;  // Very important in order to propagate exceptions
                    return;
                }

                throw new TimeoutException("The operation has timed out.");
            }
        }
    }
}