Update

Author: JamesNK

src/Servers/Kestrel/Core/src/Internal/Http3/Http3Connection.cs

@@ -453,15 +453,27 @@ private async ValueTask<Http3ControlStream> CreateNewUnidirectionalStreamAsync<T
             return new Http3ControlStream<TContext>(application, httpConnectionContext);
         }
 
-        private ValueTask<FlushResult> SendGoAway(long id)
+        private async ValueTask<FlushResult> SendGoAway(long id)
         {
+            Http3ControlStream? stream;
             lock (_sync)
             {
-                if (OutboundControlStream != null)
+                stream = OutboundControlStream;
+            }
+
+            if (stream != null)
+            {
+                try
                 {
-                    return OutboundControlStream.SendGoAway(id);
+                    return await stream.SendGoAway(id);
+                }
+                catch
+                {
+                    // The control stream may not be healthy.
+                    // Ignore error sending go away.
                 }
             }
+
             return default;
         }
 

src/Servers/Kestrel/test/InMemory.FunctionalTests/Http3/Http3ConnectionTests.cs

@@ -160,7 +160,15 @@ await WaitForConnectionErrorAsync<Http3ConnectionErrorException>(
         [Fact]
         public async Task ControlStream_ServerToClient_ErrorInitializing_ConnectionError()
         {
-            OnCreateServerControlStream = () => throw new Exception();
+            OnCreateServerControlStream = () =>
+            {
+                var controlStream = new Http3ControlStream(this, StreamInitiator.Server);
+
+                // Make server connection error when trying to write to control stream.
+                controlStream.StreamContext.Transport.Output.Complete();
+
+                return controlStream;
+            };
 
             await InitializeConnectionAsync(_noopApplication);
 

src/Servers/Kestrel/test/InMemory.FunctionalTests/Http3/Http3TestBase.cs

@@ -187,13 +187,16 @@ internal async ValueTask<Http3ControlStream> GetInboundControlStream()
             if (_inboundControlStream == null)
             {
                 var reader = MultiplexedConnectionContext.ToClientAcceptQueue.Reader;
-                while (await reader.WaitToReadAsync())
+                while (await reader.WaitToReadAsync().DefaultTimeout())
                 {
                     while (reader.TryRead(out var stream))
                     {
                         _inboundControlStream = stream;
                         var streamId = await stream.TryReadStreamIdAsync();
-                        Debug.Assert(streamId == 0, "StreamId sent that was non-zero, which isn't handled by tests");
+
+                        // -1 means stream was completed.
+                        Debug.Assert(streamId == 0 || streamId == -1, "StreamId sent that was non-zero, which isn't handled by tests");
+
                         return _inboundControlStream;
                     }
                 }