Apollo Server on Firebase Functions

graphql.ts

import * as functions from 'firebase-functions'
import {ApolloServer, gql} from 'apollo-server-cloud-functions'

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

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

const server = new ApolloServer({
  typeDefs,
  resolvers,
  playground: true,
  introspection: true,
})

export const graphql = functions.https.onRequest(server.createHandler())