Add UniTask.WithCancellation

src/UniTask.NetCoreTests/WithCancellationTest.cs

@@ -0,0 +1,40 @@
+using Cysharp.Threading.Tasks;
+using FluentAssertions;
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace NetCoreTests
+{
+    public class WithCancellationTest
+    {
+        [Fact]
+        public async Task Standard()
+        {
+            CancellationTokenSource cts = new CancellationTokenSource();
+
+            var v = await UniTask.Run(() => 10).WithCancellation(cts.Token);
+
+            v.Should().Be(10);
+        }
+
+        [Fact]
+        public async Task Cancel()
+        {
+            CancellationTokenSource cts = new CancellationTokenSource();
+
+            var t = UniTask.Create(async () =>
+            {
+                await Task.Delay(TimeSpan.FromSeconds(1));
+                return 10;
+            }).WithCancellation(cts.Token);
+
+            cts.Cancel();
+
+            (await Assert.ThrowsAsync<OperationCanceledException>(async () => await t)).CancellationToken.Should().Be(cts.Token);
+        }
+    }
+}