我如何退订正在使用reacthooks的bluebird中的诺言？

useEffect(() => {
    let isFetchable = !!qualifiedURL;

    const fetchData = async () => {
      let fetcher = Promise.resolve();

      if (isFetchable && !data) {
        setLoading(true);

       if (method === 'GET') {
          fetcher = fetch(method, qualifiedURL);
        } else {
          fetcher = fetch(method, qualifiedURL, {
              ...options,
          });
        }

        fetcher.then((result) => {
          setError(null);
          setData(result);
          setHook(result);
        }).catch((err) => {
          setData(null);
          setError(parseError(err));
        }).finally(() => {
          setLoading(false);
        });
      }

      return fetcher;
    };

    fetchData();

    return () => {
      isFetchable = false;
    };
  }, [qualifiedURL]);