server.js

const express = require('express')
const next = require('next')
const {createProxyMiddleware } = require('http-proxy-middleware')

const baseUrl = process.env.DEPLOY_MODE === 'prod' ? process.env.MAIN_BACKEND : process.env.DEPLOY_MODE === 'test' ? process.env.TEST_BACKEND : process.env.DEV_BACKEND   // 192.168.1.10:9080 local url for testing
const devProxy = {
    '/api': {
        target: baseUrl,
        pathRewrite: {
            '^/api': ''
        },
        changeOrigin: true
    }
}

const port = parseInt(process.env.PORT, 10) || 3000
const dev = process.env.NODE_ENV !== 'production'

const app = next({
    dev
})
const handle = app.getRequestHandler()

app.prepare()
    .then(() => {
        const server = express()
        if (devProxy) {
            Object.keys(devProxy).forEach(function(context) {
                server.use(createProxyMiddleware(context, devProxy[context]))
            })
        }

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

        server.listen(port, err => {
            if (err) {
                throw err
            }
            console.log(`> Ready on http://localhost:${port}`)
        })
    })
    .catch(err => {
        console.log('An error occurred, unable to start the server')
        console.log(err)
    })