express js app with nignx reverse proxy 'redirected you too many times.'

im using pm2 to run my MERN app as a proccess, when i type curl http://localhost:3000 in the console the output is indeed from my app. but nginx reverse proxy is not working. the app is running on a vps and connected to a domain name. but im getting 'redirected you too many times.' from the browser.

server.js

const PORT = 3000
const app = express()

const router = express.Router()

const { persistor, store } = createPersistor()

const serverRenderer = (req, res, next) => {

 app.get('/*', function (req, res) {
   res.sendFile(path.join(__dirname, '../build/index.html'), function (err) {
     if (err) {
       res.status(500).send(err)
     }
   })
 })

 const context = {}

 fs.readFile(path.resolve('./build/index.html'), 'utf8', (err, data) => {
   if (err) {
     console.error(err)
     return res.status(500).send('An error occurred')
   }
   return res.send(
     data.replace(
       '<div id="root"></div>',
       `<div id="root">
       ${ReactDOMServer.renderToString(
         <Provider store={store}>
           <StaticRouter location={req.url} context={context}>
             <PersistGate loading={null} persistor={persistor}>
               <App />
             </PersistGate>
           </StaticRouter>
         </Provider>
       )}
       </div>`
     )
   )
 })
}

router.use('^/$', serverRenderer)

router.use(
  express.static(path.resolve(__dirname, '..', 'build'))
)

app.use(router)

app.listen(PORT, () => {
  console.log(`SSR running on port ${PORT}`)
})

nginx/sites-available/default:

server {
listen 80 default_server;
listen [::]:80 default_server;

server_name 198.51.100.255;
return 302 $scheme://mysite.com$request_uri;

location / {
    # First attempt to serve request as file, then
    # as directory, then fall back to displaying a 404.
    try_files $uri $uri/ =404;
    proxy_pass http://localhost:3000;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection 'upgrade';
    proxy_set_header Host $host;
    proxy_cache_bypass $http_upgrade;
 }
}

and there is no error log.

note: i didnt configure SSL yet.