NodeJS + ExpressJS User Login - node.js

Question

I am currently working on a web application that requires an user login snippet. I have built an API for getting user information and others. But I cannot let NodeJS work with sessions.
So, I have an API endpoint like this for logging in: /api/v1/login
The other endpoints of the API works with an Authorization header that contains Token e3f0d20dae2da4e3f0d20dae2da4 value.
What I want to do is, when user not logged in, redirect them to login page and when an user gives their credentials POST JSON data to /api/v1/login and save the returning Token object from body and use it on other API calls.
Login endpoint returns this:
{"token" e3f0d20dae2da4e3f0d20dae2da4: , "user_id": 1104}
Well actually I have let people in and use that token for request but the problem that i am having is when there are two or more user, req.session value overrides to the latest user that logged in.
How can i let it work?
Thanks.
EDIT:
var express = require('express');
var session = require('express-session');
var router = express.Router();
var https = require('https');
var url = require('url');
var request = require('request');
var cookieParser = require("cookie-parser");
var FileStore = require('session-file-store')(session);
var sessionMW = session(
{
store: FileStore(),
secret: '$LSvj3KLSv2$$1!skv!!!!xxIf3eef5Fxc',
cookie: { maxAge: 36000, httpOnly: false },
resave: false,
saveUninitialized: false
});
router.get('/api/:endpoint/:first?/:second?/:third?', sessionMW, function(req, res, next) {
if(sess.token){
// make http request and return json data from server
} else {
// fail
}
router.post("/login", sessionMW, function(req, res, next){
var username = req.body.username;
var password = req.body.password;
var options = {
url: endpoints.login_request(),
method: 'POST',
json: {
"username" : username,
"password" : password
},
headers: {
'User-Agent' : 'Agent',
'Content-Type': 'application/json'
}
};
request(options, function(err, response, body) {
if(body.error){
res.send('{error:1}');
} else if(body.token) {
req.session.token = body.token;
req.session.user_id = body.user_id;
res.writeHead(302, {
'Location': '/#/home'
//add other headers here...
});
}
console.log(req.session);
res.end();
});
});