A cancellation doesn't work in some cases and a deadlock may occure. …

src/Docker.DotNet/Endpoints/StreamUtil.cs

@@ -19,7 +19,7 @@ internal static async Task MonitorStreamAsync(Task<Stream> streamTask, DockerCli
                     using (var reader = new StreamReader(stream, new UTF8Encoding(false)))
                     {
                         string line;
-                        while ((line = await reader.ReadLineAsync()) != null)
+                        while ((line = await reader.ReadLineAsync().WithCancellation(cancel)) != null)
                         {
                             progress.Report(line);
                         }
@@ -40,7 +40,7 @@ internal static async Task MonitorStreamForMessagesAsync<T>(Task<Stream> streamT
                         string line;
                         try
                         {
-                            while ((line = await reader.ReadLineAsync()) != null)
+                            while ((line = await reader.ReadLineAsync().WithCancellation(cancel)) != null)
                             {
                                 var prog = client.JsonSerializer.DeserializeObject<T>(line);
                                 if (prog == null) continue;
@@ -57,5 +57,19 @@ internal static async Task MonitorStreamForMessagesAsync<T>(Task<Stream> streamT
                 }
             }
         }
+
+        private 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;
+        }
     }
 }

test/Docker.DotNet.Tests/ISystemOperations.Tests.cs

@@ -90,6 +90,17 @@ public async Task MonitorEventsAsync_Succeeds()
             await _client.Images.DeleteImageAsync($"{repository}:{tag}", new ImageDeleteParameters());
         }
 
+        [Fact]
+        public async Task MonitorEventsAsync_EmptyContainersList_CanBeCancelled()
+        {
+            var cts = new CancellationTokenSource();
+
+            cts.CancelAfter(1000);
+            var task = _client.System.MonitorEventsAsync(new ContainerEventsParameters(), new Progress(), cts.Token);
+
+            await Assert.ThrowsAsync<OperationCanceledException>(async () => await task);
+        }
+
         class Progress : IProgress<JSONMessage>
         {
             internal Action<JSONMessage> _onCalled;