不工作在Heroku阿波罗服务器操场（本地工作）(Apollo server playground

我试图部署运行节点JS在Heroku上的应用程序，它已成功部署，但操场上似乎并不工作。

我来解决此解决方案通过设置introspection: true ： https://github.com/apollographql/apollo-server/issues/1718但也似乎并不工作。

Heroku的日志

我的代码：

的package.json

{
  "name": "travelindiaserver",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "clean": "rm -rf build && mkdir build",
    "build-babel": "babel -d ./build ./src -s",
    "build": "npm run clean && npm run build-babel",
    "start": "npm run build && node ./build/index.js"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "apollo-server-express": "^2.4.8",
    "babel-preset-env": "^1.7.0",
    "express": "^4.16.4",
    "graphql": "^14.2.1"
  },
  "devDependencies": {
    "babel-cli": "^6.26.0"
  }
}

index.js

import express from "express";
import { ApolloServer } from "apollo-server-express";

import typeDefs from "./schema";
import resolvers from "./resolvers";
import models from "./models";

const app = express();

const server = new ApolloServer({
  typeDefs,
  resolvers,
  context: { models },
  introspection: true
});

server.applyMiddleware({ app });

const PORT = process.env.PORT || 5000;

app.listen(PORT, () =>
  console.log(
    `