"ObjectDisposedException: Safe handle has been closed" when running FunctionalTests on OSX

[mikeharder]

The following exception was thrown once when running FunctionalTests on OSX. No test failures were reported before the exception:

Unhandled Exception: System.ObjectDisposedException: Safe handle has been closed
   at System.Runtime.InteropServices.SafeHandle.DangerousAddRef(Boolean& success)
   at System.StubHelpers.StubHelpers.SafeHandleAddRef(SafeHandle pHandle, Boolean& success)
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Networking.Libuv.NativeMethods.uv_async_send(UvAsyncHandle handle)
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Networking.Libuv.async_send(UvAsyncHandle handle)
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Networking.UvAsyncHandle.Send()
   at Microsoft.AspNetCore.Server.Kestrel.Internal.KestrelThread.PostCloseHandle(Action`1 callback, IntPtr handle)
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Networking.UvHandle.ReleaseHandle()
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Networking.UvStreamHandle.ReleaseHandle()
   at System.Runtime.InteropServices.SafeHandle.InternalFinalize()
   at System.Runtime.InteropServices.SafeHandle.Finalize()

[Tragetaschen]

That's the same stack trace as in #946. Do those tests properly dispose Kestrel?

[halter73]

@Tragetaschen The tests do dispose KestrelServer. It's somewhat harder to mess that up in the functional tests where we pretty much always use using (WebHostBuilder.Build()). The error happens fairly infrequently, and looks like it could be due to some sort of shutdown race.