code: function cbk(err, fields, files, resolve) {
      let fileList;
  
      if (err) {
        debug('upload file error:' + err);
      } else {
        try {
          fileList = createFilenameHash(config.uploadDir, files);
          debug('upload file success！');
        } catch (err) {
          fileList = files;
          debug('create filename hash:' + err);
        }
      }
  
      resolve(fileList);
    }
docs: cbk
  @param  {Object} err    错误信息
  @param  {Object} fields
  @param  {Object} files  上传的文件