Fix call to cleanup

Author: martinRenou

jupyter_server/base/handlers.py

@@ -212,6 +212,10 @@ def jinja_template_vars(self):
         """User-supplied values to supply to jinja templates."""
         return self.settings.get("jinja_template_vars", {})
 
+    @property
+    def serverapp(self):
+        return self.settings["serverapp"]
+
     # ---------------------------------------------------------------
     # URLs
     # ---------------------------------------------------------------

jupyter_server/services/shutdown.py

@@ -11,7 +11,7 @@ class ShutdownHandler(JupyterHandler):
     async def post(self):
         self.log.info("Shutting down on /api/shutdown request.")
 
-        await self._cleanup()
+        await self.serverapp._cleanup()
 
         ioloop.IOLoop.current().stop()