Webpack server HMR issue

app.js

import express from 'express'

const app = express()

app.use((req, res, next) => {
  console.log('ping')
  next()
})

export default app

index.js

import http from 'http'
import app from './app'

let currentApp = app
const server = http.createServer(currentApp)

server.listen(8080, () => console.log('Server established')

if (module.hot) {
  // Whenever hot update happens in "app"
  module.hot.accepts(['./app'], () => {
    // Stop serving the outdated app
    server.removeListener('request', currentApp)
    
    // Require the updated app module
    const app = require('./app').default
    
    // Start serving the updated app
    server.on('request', app)
    currentApp = app
  })
}

I also use "start-server-webpack-plugin": "^2.2.5" that spawns an actual built server automatically and signals updates.

The setup above provides hot module replacement for the server, but appends multiple instances of the same app middleware upon hot updates. Each update appends a new middleware, resulting into:

middlewareCount = updates + 1

Is there something wrong with this hot update declaration? How to ensure that app is thrown away and re-created upon hot update?