Aiohttp client session and FastAPI DI

asgi.py

from di import ClientSessionManager, provide_client_session_stub, provide_client_session


async def on_shutdown() -> None:
    await ClientSessionManager.close()


def build_asgi_application() -> FastAPI:
  application = FastAPI(on_shutdown=[on_shutdown])
  
  app.dependency_overrides[provide_client_session_stub] = provide_client_session
  
  return app

di.py

import aiohttp


class ClientSessionManager:
  _client_session: aiohttp.ClientSession | None = None

  @property
  def client_session(self) -> aiohttp.ClientSession:
    return self.build()

  @classmethod
  def build(cls) -> aiohttp.ClientSession:
    if not cls._client_session:
      cls._client_session = aiohttp.ClientSession()
    return cls._client_session
    
  @classmethod
  async def close(cls) -> None:
    if cls._client_session:
      await cls._client_session.close()
      cls._client_session = None


def provide_client_session_stub():
  ...


def provide_client_session() -> aiohttp.ClientSession:
  return ClientSessionManager.client_session