async request(api, opts) {
    const options = Object.assign({
      dataType: 'json',
      timeout: [ '30s', '30s' ],
    }, opts);

    const result = await this.ctx.curl(`${this.serverUrl}/${api}`, options);
    return result.data;
  }
request hacker-news api
@param {String} api - Api name
@param {Object} [opts] - urllib options
@return {Promise} response.data