test(batch25): port gateway connect and tls baseline tests

dotnet/tests/ZB.MOM.NatsNet.Server.Tests/ImplBacklog/ConcurrencyTests2.Impltests.cs

@@ -506,5 +506,28 @@ public sealed partial class ConcurrencyTests2
         }
     }
 
+    [Fact] // T:2490
+    public void NoRaceConnectionObjectReleased_ShouldSucceed()
+    {
+        var server = NatsServer.NewServer(new ServerOptions
+        {
+            Gateway = new GatewayOpts { Name = "A", Port = 5222 },
+        }).Server;
+
+        try
+        {
+            var outbound = new ClientConnection(ZB.MOM.NatsNet.Server.Internal.ClientKind.Gateway, server) { Cid = 42 };
+            server.RegisterOutboundGatewayConnection("B", outbound);
+            server.GetOutboundGatewayConnection("B").ShouldNotBeNull();
+
+            outbound.CloseConnection(ClosedState.ClientClosed);
+            outbound.IsClosed().ShouldBeTrue();
+        }
+        finally
+        {
+            server.Shutdown();
+        }
+    }
+
     private static string NewRoot() => Path.Combine(Path.GetTempPath(), $"impl-fs-c2-{Guid.NewGuid():N}");
 }