chore: cancel pending tasks before db disconnect on shutdown

bot.py

@@ -1,3 +1,5 @@
+import asyncio
+
 import nonebot
 
 # from nonebot.adapters.discord import Adapter as DiscordAdapter
@@ -16,7 +18,28 @@ driver.register_adapter(OneBotV11Adapter)
 
 from zhenxun.services.db_context import disconnect
 
+
+async def cancel_pending_tasks():
+    """在关闭前尽量取消仍在运行的协程，避免关闭后继续访问数据库连接池。"""
+    loop = asyncio.get_running_loop()
+    current = asyncio.current_task(loop=loop)
+    pending = [
+        task
+        for task in asyncio.all_tasks(loop)
+        if task is not current and not task.done()
+    ]
+    if not pending:
+        return
+
+    for task in pending:
+        task.cancel()
+
+    await asyncio.gather(*pending, return_exceptions=True)
+
+
 # driver.on_startup(init)
+# 先取消可能在跑的任务，再断开数据库，避免 pool closing 异常
+driver.on_shutdown(cancel_pending_tasks)
 driver.on_shutdown(disconnect)
 
 # nonebot.load_builtin_plugins("echo")