`execute` returns a [`MaybeAwaitable`](https://github.com/graphql-python/graphql-core-next/blob/3de6454304422b3cd832cb1bb075be202e26616c/graphql/execution/execute.py#L115) but `subscribe` doesn't await it if it does. https://github.com/graphql-python/graphql-core-next/blob/3de6454304422b3cd832cb1bb075be202e26616c/graphql/subscription/subscribe.py#L67-L87