AsyncLock improvements and additional tests

Author: andrewvk

Main/src/Threading/AsyncLock.cs

@@ -72,6 +72,15 @@ public Task<IDisposable> Acquire(int timeout, CancellationToken cancellation) =>
 		[ItemNotNull]
 		public Task<IDisposable> Acquire(TimeSpan timeout) => Acquire(timeout, CancellationToken.None);
 
+		/// <summary>
+		/// Acquires async lock.
+		/// </summary>
+		/// <param name="cancellation">The CancellationToken token to observe.</param>
+		/// <returns>A task that returns <see cref="IDisposable"/> to release the lock.</returns>
+		[NotNull]
+		[ItemNotNull]
+		public Task<IDisposable> Acquire(CancellationToken cancellation) => Acquire(-1, cancellation);
+
 		/// <summary>
 		/// Acquires async lock.
 		/// </summary>

Main/tests/Threading/AsyncLockTest.cs

@@ -1,5 +1,8 @@
-using System.Diagnostics;
+using System;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 
 using NUnit.Framework;
@@ -39,5 +42,36 @@ await Enumerable
 			Assert.IsFalse(opActive);
 			Assert.GreaterOrEqual(sw.ElapsedMilliseconds, time * count + timeInc * count / 2);
 		}
+
+		[Test]
+		[SuppressMessage("ReSharper", "MethodSupportsCancellation")]
+		public async Task Cancellation()
+		{
+			var cts = new CancellationTokenSource();
+			var lck = new AsyncLock();
+			const int delay = 5000;
+			const int ensureLockInterval = 30;
+			Task.Run(
+				async () =>
+				{
+					using (await lck.Acquire())
+						await Task.Delay(delay);
+				});
+			await Task.Delay(ensureLockInterval);
+			var sw = Stopwatch.StartNew();
+			var task = Task.Run(
+				async () =>
+				{
+					using (await lck.Acquire(cts.Token))
+						sw.Stop();
+				});
+			cts.Cancel();
+			try
+			{
+				await task;
+			}
+			catch (TaskCanceledException) {}
+			Assert.Less(sw.ElapsedMilliseconds, delay - ensureLockInterval);
+		}
 	}
 }