Fix compatibility with Python 3.10, refs #358 (#359)

Co-authored-by: Andrew Svetlov <andrew.svetlov@gmail.com>

.github/workflows/ci.yml

@@ -43,7 +43,7 @@ jobs:
     needs: lint
     strategy:
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9]
+        python-version: ["3.6", "3.7", "3.8", "3.9", "3.10"]
         os: [ubuntu]
       fail-fast:
         false

janus/__init__.py

@@ -1,4 +1,5 @@
 import asyncio
+import sys
 import threading
 from asyncio import QueueEmpty as AsyncQueueEmpty
 from asyncio import QueueFull as AsyncQueueFull
@@ -36,6 +37,9 @@ def __init__(self, maxsize: int = 0) -> None:
         self._all_tasks_done = threading.Condition(self._sync_mutex)
 
         self._async_mutex = asyncio.Lock()
+        if sys.version_info[:3] == (3, 10, 0):
+            # Workaround for Python 3.10 bug, see #358:
+            getattr(self._async_mutex, '_get_loop', lambda: None)()
         self._async_not_empty = asyncio.Condition(self._async_mutex)
         self._async_not_full = asyncio.Condition(self._async_mutex)
         self._finished = asyncio.Event()