rn-fetch-blob取消下载-承诺拒绝

Question

我使用rn-fetch-blob在React Native中下载文件 一切正常，但根据文档使用cancel method时，取消操作无效并出现错误“ fileFetchPromise无法定义”

我的代码：

const download = () => {
  let fileOptions = { fileCache: true, path: path, };
  const fileFetchPromise = config(fileOptions).fetch('GET', fileUrl);
  fileFetchPromise.progress({ interval : 1000 }, (received, total) => {
    let persend = 100 * received / total;
    setSaved(persend.toFixed(0));
    setReceived(bytesToSize(received));
    setTotalSize(bytesToSize(total));
  });

  fileFetchPromise.then((data) => {
    setSaved('100');
  }).catch((err) => {
    setSaved('0')
  })
}

const cancelDownload = () => {
  fileFetchPromise.cancel((err) => {})
}

如何取消（中止）获取？