Any next read or write will be done from that position.

        To be awaitable, compatible with async, this is run in threadpool.
        """
        return await super().seek(offset)

    async def close(self) -> None:
        """
        Close the file.

        To be awaitable, compatible with async, this is run in threadpool.
        """
        return await super().close()

# dependencies' AsyncExitStack
def request_response(
    func: Callable[[Request], Union[Awaitable[Response], Response]],
) -> ASGIApp:
    """
    Takes a function or coroutine `func(request) -> response`,
    and returns an ASGI application.
    """
    f: Callable[[Request], Awaitable[Response]] = (
        func if is_async_callable(func) else functools.partial(run_in_threadpool, func)  # type:ignore
    )