Using Apollo Server 2 with GraphiQL instead of GraphQL Playground

index.js

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

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

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

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

const app = express();

app.get('/graphql', graphqlHTTP({
  schema: typeDefs,
  graphiql: true
}));

server.applyMiddleware({ app });

app.listen({ port: 4000 }, () =>
  console.log(`Apollo Server ready at http://localhost:4000${server.graphqlPath}`)
);