App uses lifespan context manager for startup + shutdown

tiled/server/app.py

@@ -5,6 +5,7 @@
 import secrets
 import sys
 import urllib.parse
+from contextlib import asynccontextmanager
 from functools import lru_cache, partial
 from pathlib import Path
 from typing import List
@@ -195,7 +196,14 @@ def build_app(
                 )
         # If we reach here, the no configuration problems were found.
 
-    app = FastAPI()
+    @asynccontextmanager
+    async def lifespan(app: FastAPI):
+        "Manage lifespan events for each event loop that the app runs in"
+        await startup_event()
+        yield
+        await shutdown_event()
+
+    app = FastAPI(lifespan=lifespan)
 
     if SHARE_TILED_PATH:
         # If the distribution includes static assets, serve UI routes.
@@ -465,7 +473,6 @@ def override_get_settings():
             settings.database_uri = settings.database_uri or "sqlite+aiosqlite://"
         return settings
 
-    @app.on_event("startup")
     async def startup_event():
         # Validate the single-user API key.
         settings = app.dependency_overrides[get_settings]()
@@ -668,7 +675,6 @@ async def purge_expired_sessions_and_api_keys():
                 asyncio.create_task(purge_expired_sessions_and_api_keys())
             )
 
-    @app.on_event("shutdown")
     async def shutdown_event():
         # Run shutdown tasks collected from trees (adapters).
         for task in tasks.get("shutdown", []):