docs: @Override
      public <T> T call() throws Exception {
  
          // 删除临时文件
          // LOGGER.info("start to remove tmp download file: " + ""
          // + localTmpFile.getAbsolutePath());
          if (localTmpFile.exists()) {
              localTmpFile.delete();
          }
  
          // start tp download
          LOGGER.debug("start to download. From: " + remoteUrl + " , TO: " + localTmpFile.getAbsolutePath());
  
          // 下载
          FileUtils.copyURLToFile(remoteUrl, localTmpFile);
  
          // check
          if (!OsUtil.isFileExist(localTmpFile.getAbsolutePath())) {
              throw new Exception("download is ok, but cannot find downloaded file." + localTmpFile);
          }
  
          // download success
          LOGGER.debug("download success!  " + localTmpFile.getAbsolutePath());
  
          return null;
      }