simplified notification code

src/pwo/notification.py

@@ -1,5 +1,5 @@
 from .private import AsyncQueueIterator
-from asyncio import Queue, AbstractEventLoop, Future, CancelledError
+from asyncio import Queue, AbstractEventLoop, Future, CancelledError, timeout
 from typing import Callable, Optional
 from logging import getLogger
 
@@ -23,25 +23,16 @@ class Subscriber:
         self._unsubscribe_callback(self)
         log.debug('Deleted subscriber %s', id(self))
 
-    async def wait(self, tout: float) -> bool:
-        self._event = self._loop.create_future()
+    async def wait(self, tout: Optional[float]) -> bool:
 
-        def callback() -> None:
-            evt = self._event
-            if evt is None:
-                raise ValueError('Event is None')
-            evt.cancel()
-            if not evt.done():
-                evt.set_result(False)
-
-        handle = self._loop.call_later(tout, callback)
+        future = self._loop.create_future()
+        self._event = future
         try:
-            log.debug('Subscriber %s is waiting for an event', id(self))
-            return await self._event
-        except CancelledError:
+            async with timeout(tout):
+                log.debug('Subscriber %s is waiting for an event', id(self))
+                await future
+        except TimeoutError:
             return False
-        finally:
-            handle.cancel()
 
     def notify(self) -> None:
         log.debug('Subscriber %s notified', id(self))