Fix weak reference Kestrel test

src/Servers/Kestrel/test/InMemory.FunctionalTests/HttpConnectionManagerTests.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Diagnostics;
+using System.Runtime.CompilerServices;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Infrastructure;
@@ -56,14 +57,10 @@ public async Task CriticalErrorLoggedIfApplicationDoesntComplete()
         },
         testContext))
         {
-            using (var connection = server.CreateConnection())
-            {
-                await connection.SendEmptyGet();
-
-                Assert.True(await appStartedWh.WaitAsync(TestConstants.DefaultTimeout));
-
-                // Close connection without waiting for a response
-            }
+            // Create the connection in a separate non-inlined method so that the connection
+            // and any locals it references aren't kept rooted on this method's stack frame,
+            // which would prevent HttpConnection from being garbage collected.
+            await CreateConnectionAndSendRequest(server, appStartedWh);
 
             var logWaitAttempts = 0;
 
@@ -77,6 +74,19 @@ public async Task CriticalErrorLoggedIfApplicationDoesntComplete()
         }
     }
 
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static async Task CreateConnectionAndSendRequest(TestServer server, SemaphoreSlim appStartedWh)
+    {
+        using (var connection = server.CreateConnection())
+        {
+            await connection.SendEmptyGet();
+
+            Assert.True(await appStartedWh.WaitAsync(TestConstants.DefaultTimeout));
+
+            // Close connection without waiting for a response
+        }
+    }
+
     private class CallbackLoggerProvider : ILoggerProvider
     {
         private readonly Action<EventId> _logAction;