如何使用Apollo服务器提供index.html文件？

npm init -y

npm install apollo-server express

const { ApolloServer, gql } = require('apollo-server');
const express = require('express');
const path = require('path');

const typeDefs = gql`
  type Query {
    hello: String
  }
`;

const resolvers = {
  Query: {
    hello: () => 'Hello, World!'
  }
};

const server = new ApolloServer({ typeDefs, resolvers });

const app = express();
server.applyMiddleware({ app });

app.get('/', (req, res) => {
  res.sendFile(path.join(__dirname, 'index.html'));
});

app.listen({ port: 3000 }, () =>
  console.log(`Server running at http://localhost:3000${server.graphqlPath}`)
);

node server.js