Sessions not working on post requests?

Question

Node.js

Hello everyone, I think it's been 8 hours on a simple task.
I use express-session with these settings:
resave: true,
saveUninitialized: false,
secret: 'splashsecretsession',
store: new FileStore(),
cookie : { secure : false, maxAge : (4 * 60 * 60 * 1000), httpOnly: false }
If doing
Router.get('/login', sessionMiddleware, (request, response, next) => {
console.log(request.session);
request.session.test = 'test3';
request.session.save ();
Everything works. By opening /login 2 times, I will see the saved session.
But if you change .get to .post and call this request, then the session is not saved. More precisely, each time it is saved as a new one and reset to zero when it is called again. You need to somehow save the POST session