Cleanly close aiohttp session on exit

arkhamdb.py

@@ -1,3 +1,4 @@
+import asyncio
 from typing import Any
 
 import aiohttp
@@ -8,19 +9,27 @@ ArkhamDBDeck = Any  # TODO: better typing
 
 
 class ArkhamDBClient:
-    session: aiohttp.ClientSession
+    _session: aiohttp.ClientSession
 
     origin: str
 
     def __init__(self, arkhamdb_origin: str = ARKHAMDB_ORIGIN):
-        self.session = aiohttp.ClientSession()
+        self._session = aiohttp.ClientSession()
         self.origin = arkhamdb_origin
 
+    def __del__(self):
+        loop = asyncio.get_event_loop()
+        loop.run_until_complete(self.close())
+
+    async def close(self):
+        await self._session.close()
+
     async def get_latest_deck(self, deck_id: int) -> ArkhamDBDeck:
         next_deck_id = deck_id
         deck = None
         while deck is None or deck["next_deck"] is not None:
-            async with self.session.get(self.origin + f"/api/public/deck/{next_deck_id}.json") as resp:
+            async with self._session.get(
+                    self.origin + f"/api/public/deck/{next_deck_id}.json") as resp:
                 deck = await resp.json()
                 next_deck_id = deck["next_deck"]