add code to call a shutdown function to allow implementations to clean up

wsfwd/__init__.py

@@ -3,7 +3,7 @@ import contextlib
 import functools
 import json
 import unittest
-from unittest.mock import Mock, AsyncMock
+from unittest.mock import patch, Mock, AsyncMock
 
 PIPE = object()
 
@@ -271,6 +271,15 @@ class WSFWDCommon:
 	async def __aexit__(self, exc_type, exc, tb):
 		self._task.cancel()
 
+		await self.shutdown()
+
+	async def shutdown(self):
+		'''
+		Called to clean up resources allocated.
+		'''
+
+		pass
+
 	async def _sendcmd(self, cmd):
 		'''
 		Internal function for sending the dict in cmd.  This
@@ -396,6 +405,16 @@ class Test(unittest.IsolatedAsyncioTestCase):
 	def runFakeServer(self, func):
 		return asyncio.create_task(func(self.toserver.get, self.toclient.put))
 
+	@timeout(2)
+	@patch('wsfwd.WSFWDCommon.shutdown')
+	async def test_shutdown(self, shut):
+		# make sure that a with block
+		async with WSFWDCommon(None, None) as st:
+			pass
+
+		# calls shutdown
+		shut.assert_called()
+
 	@timeout(2)
 	async def test_authfail(self):
 		async def fake_server(reader, writer):