Express session not saved from page to page

I am trying to save sessions, but when I make a session, there is no next request.

When I send an ajax request to /login

, I establish a session with req.session.username

and then send back the object that says {success:true}

. Then I refresh the page, and if the username exists in the session, I show the user page, otherwise I show the master page.

Every time I refresh the page in /

, it always shows the login even after submitting a request to /login

and establishing a session. Why is the session not being saved?

let express = require('express')
let sessions = require('express-session')
let bodyParser = require('body-parser')
let app = express()

app.use(sessions({
  secret: 'connection-id',
  resave: true,
  saveUninitialized: true,
  cookie: { maxAge: 60000 }
}))

app.use(bodyParser.json())

app.get('/', (req, res) => {
  if (req.session.username) {
    res.render('pages/home')
  } else {
    res.render('pages/index')
  }
}).post('/login', (req, res) => {
  if (req.xhr) {
    req.session.username = req.body.username
    res.send({ success: true })
  } else {
    res.sendStatus(500)
  }
})

      

        
        
        
      

    

Client side:

let response = await fetch('/login', {
  method: 'post',
  headers: {
    'X-Requested-With': 'XMLHttpRequest',
    'Accept': 'application/json',
    'Content-Type': 'application/json'
  },
  body: new FormData((document.getElementById('login-form'))).toJson()
})

let json = await response.json()
if (json.success) {
  window.location.href = '/'
}

      

        
        
        
      

    

When I make an Ajax request, I return the following header:

set-cookie:connect.sid=s%3At25S_TmjwL6vVkhyJ9LuKIyy4EH1LTcy.Zu4fBpMibfjmMofxQI5K%2FmgAYHWFqQf3x8HPzcQbDH4; Path=/; Expires=Sun, 23 Jul 2017 15:29:26 GMT; HttpOnly

      

        
        
        
      

    

Edit

So, after commenting out everything in my code and slowly splitting and testing the lines, I found that this doesn't work:

req.session.username = req.body.username // body.username Contains a string

      

        
        
        
      

    

However, this works:

req.session.username = 'Billy'

      

        
        
        
      

    

I'm not sure why he does this. Any suggestions?