Added backport for Task.WaitAsync()

src/Common/Threading/ResultRacer.cs

@@ -83,18 +83,7 @@ public T GetResult()
     /// Waits until at least one call to <see cref="TrySetResult"/> or <see cref="TrySetResultAsync"/> succeeded and returns its result.
     /// </summary>
     public async Task<T> GetResultAsync()
-    {
-        var task = _completion.Task;
-#if NET
-        return await task.WaitAsync(cancellationToken);
-#else
-        var cancellationCompletion = new TaskCompletionSource<bool>();
-        using (cancellationToken.Register(() => cancellationCompletion.SetCanceled()))
-            await Task.WhenAny(task, cancellationCompletion.Task);
-        cancellationToken.ThrowIfCancellationRequested();
-        return await task;
-#endif
-    }
+        => await _completion.Task.WaitAsync(cancellationToken);
 }
 
 /// <summary>

src/Common/Threading/TaskExtensions.cs

@@ -0,0 +1,47 @@
+// Copyright Bastian Eicher
+// Licensed under the MIT License
+
+#if !NET20 && !NET40
+using System.Threading.Tasks;
+
+namespace NanoByte.Common.Threading;
+
+public static class TaskExtensions
+{
+    /// <summary>
+    /// Gets a <see cref="Task"/> that will complete when <paramref name="task"/> completes or when the specified <paramref name="cancellationToken"/> has cancellation requested.
+    /// </summary>
+    /// <exception cref="OperationCanceledException">Cancellation has been requested.</exception>
+    public static async Task WaitAsync(this Task task, CancellationToken cancellationToken)
+#if NETFRAMEWORK
+    {
+        var cancellationCompletion = new TaskCompletionSource<bool>();
+        var token = cancellationToken;
+        using (token.Register(() => cancellationCompletion.SetCanceled()))
+            await Task.WhenAny(task, cancellationCompletion.Task);
+        token.ThrowIfCancellationRequested();
+        await task;
+    }
+#else
+        => await task.WaitAsync(cancellationToken);
+#endif
+
+    /// <summary>
+    /// Gets a <see cref="Task"/> that will complete when <paramref name="task"/> completes or when the specified <paramref name="cancellationToken"/> has cancellation requested.
+    /// </summary>
+    /// <exception cref="OperationCanceledException">Cancellation has been requested.</exception>
+    public static async Task<T> WaitAsync<T>(this Task<T> task, CancellationToken cancellationToken)
+#if NETFRAMEWORK
+    {
+        var cancellationCompletion = new TaskCompletionSource<bool>();
+        var token = cancellationToken;
+        using (token.Register(() => cancellationCompletion.SetCanceled()))
+            await Task.WhenAny(task, cancellationCompletion.Task);
+        token.ThrowIfCancellationRequested();
+        return await task;
+    }
+#else
+        => await task.WaitAsync(cancellationToken);
+#endif
+}
+#endif