next.js/examples/with-relay-modern-server-express/server/index.js

const express = require('express')
const graphqlHTTP = require('express-graphql')
const next = require('next')
const path = require('path')
const fs = require('fs')
const { buildSchema } = require('graphql')
const rootValue = require('./rootValue')
const port = parseInt(process.env.PORT, 10) || 3000
const dev = process.env.NODE_ENV !== 'production'
const app = next({ dev })
const handle = app.getRequestHandler()
const schemaPath = path.join(__dirname, '/schema.graphql')
const schemaContent = fs.readFileSync(schemaPath).toString()
const graphqlSchema = buildSchema(schemaContent)

app.prepare()
  .then(() => {
    const server = express()

    server.use('/graphql', graphqlHTTP({
      schema: graphqlSchema,
      graphiql: false,
      rootValue: rootValue
    }))

    server.get('*', (req, res) => {
      return handle(req, res)
    })

    server.listen(port, (err) => {
      if (err) throw err
      console.log(`> Ready on http://localhost:${port}`)
    })
  })