node.js:req.next不是函数

我已经尝试将该项目部署到谷歌云平台。代码在我的本地机器上运行良好。但是，我在gcloud上遇到以下错误

TypeError: req.next is not a function
at done (/app/node_modules/express/lib/response.js:955)
at tryRender (/app/node_modules/express/lib/application.js:641)
at EventEmitter.render (/app/node_modules/express/lib/application.js:591)
at ServerResponse.render (/app/node_modules/express/lib/response.js:960)
at (/app/routes/posts.js:15)
at tryCatcher (/app/node_modules/mongolass/node_modules/bluebird/js/release/util.js:16)
at Promise._settlePromiseFromHandler (/app/node_modules/mongolass/node_modules/bluebird/js/release/promise.js:510)
at Promise._settlePromise (/app/node_modules/mongolass/node_modules/bluebird/js/release/promise.js:567)
at Promise._settlePromise0 (/app/node_modules/mongolass/node_modules/bluebird/js/release/promise.js:612)
at Promise._settlePromises (/app/node_modules/mongolass/node_modules/bluebird/js/release/promise.js:691)
at Async._drainQueue (/app/node_modules/mongolass/node_modules/bluebird/js/release/async.js:138)
at Async._drainQueues (/app/node_modules/mongolass/node_modules/bluebird/js/release/async.js:148)
at Immediate.Async.drainQueues (async.js:17)
at runCallback (timers.js:666)
at tryOnImmediate (timers.js:639)
at processImmediate (timers.js:611)

routes/posts.js：

router.get('/', function(req, res, next) {
  var author = req.query.author;

  PostModel.getPosts(author)
    .then(function (posts) {
      res.render('posts', { //line 15
        posts: posts
      });
    })
    .catch(next);
});

getPosts功能：

getPosts: function getPosts(author) {
    var query = {};
    if (author) {
      query.author = author;
    }
    return Post
      .find(query)
      .populate({ path: 'author', model: 'User' })
      .sort({ _id: -1 })
      .addCreatedAt()
      .addCommentsCount()
      .contentToHtml()
      .exec();
  },

---

您的node.js、express等版本是否与您的开发盒完全相同？这可能不是gcloud问题，请尝试使用node_ENV=production在本地运行，并查看它是否复制node-v:v6.10.2“依赖项”：{“config lite”：“1.5.0”、“connect flash”：“0.1.1”、“connect mongo”：“1.3.2”、“ejs”：“2.5.2”、“express”：“4.14.0”，“快速强大”：“1.0.0”，“快速会话”：“1.14.2”，“快速温斯顿”：“2.0.0”，“标记”：“0.3.6”，“时刻”：“2.15.2”，“蒙古驴”：“2.3.1”，“时间戳对象”：“1.3.0”，“sha1”：“1.1.1”，“温斯顿”：“2.2.0”}我已经测试过了，效果很好。你的app.yaml看起来怎么样？所有的URL都定义得很好吗？如果你用函数（req，res，next）替换函数（req，res），会发生什么？