[release/6.0] Dispose CTS in HubConnection streaming (#51139)

* Dispose CTS in HubConnection streaming

* Apply suggestions from code review

Co-authored-by: Stephen Halter <halter73@gmail.com>

---------

Co-authored-by: Brennan <brecon@microsoft.com>
Co-authored-by: Stephen Halter <halter73@gmail.com>

src/SignalR/clients/csharp/Client.Core/src/HubConnection.cs

@@ -743,7 +743,7 @@ async Task ReadChannelStream()
                 }
             }
 
-            return CommonStreaming(connectionState, streamId, ReadChannelStream);
+            return CommonStreaming(connectionState, streamId, ReadChannelStream, tokenSource);
         }
 
         // this is called via reflection using the `_sendIAsyncStreamItemsMethod` field
@@ -760,11 +760,14 @@ async Task ReadAsyncEnumerableStream()
                 }
             }
 
-            return CommonStreaming(connectionState, streamId, ReadAsyncEnumerableStream);
+            return CommonStreaming(connectionState, streamId, ReadAsyncEnumerableStream, tokenSource);
         }
 
-        private async Task CommonStreaming(ConnectionState connectionState, string streamId, Func<Task> createAndConsumeStream)
+        private async Task CommonStreaming(ConnectionState connectionState, string streamId, Func<Task> createAndConsumeStream, CancellationTokenSource cts)
         {
+            // make sure we dispose the CTS created by StreamAsyncCore once streaming completes
+            using var _ = cts;
+
             Log.StartingStream(_logger, streamId);
             string? responseError = null;
             try