[FIX] fastapi: Ensure no default eventloop thread is created

Before this change, an eventloop thread was created on each instanciation of the ASGIMiddleware class. We want to avoid this behavior to avoid the creation of zombie threads

Author: lmignon

fastapi/middleware.py

@@ -13,12 +13,26 @@
 
 import a2wsgi
 from a2wsgi.asgi import ASGIResponder
+from a2wsgi.asgi_typing import ASGIApp
 from a2wsgi.wsgi_typing import Environ, StartResponse
 
 from .pools import event_loop_pool
 
 
 class ASGIMiddleware(a2wsgi.ASGIMiddleware):
+    def __init__(
+        self,
+        app: ASGIApp,
+        wait_time: float | None = None,
+    ) -> None:
+        # We don't want to use the default event loop policy
+        # because we want to manage the event loop ourselves
+        # using the event loop pool.
+        # Since the the base class check if the given loop is
+        # None, we can pass False to avoid the initialization
+        # of the default event loop
+        super().__init__(app, wait_time, False)
+
     def __call__(
         self, environ: Environ, start_response: StartResponse
     ) -> Iterable[bytes]: