code: function loadBootstrap(appPath, modules, type = 'worker') {
    let bootstrapPath = '';
    if (modules.length) {
      bootstrapPath = path.join(appPath, 'common/bootstrap');
    } else {
      bootstrapPath = path.join(appPath, 'bootstrap');
    }
    const filepath = path.join(bootstrapPath, `${type}.js`);
    if (helper.isFile(filepath)) {
      debug(`load file: ${filepath}`);
      return require(filepath);
    }
  }
docs: load bootstrap files