how to get the api result from middleware to routes

You call next immediate in your middleware, now res.locals.wallet value is undefined.

Just call next when you finish the job (call api).

var request = require('request');

module.exports = function(req, res, next) {

    if(req.session.active){
        res.locals.active = req.session.active;
        res.locals.email = req.session.email;
        // res.locals.wallet = req.session.wallet;
        res.locals.admin = req.session.admin;
        res.locals.cart = req.session.cart;
        res.locals.partner = req.session.partner;

        var data =  {
            user_id :req.session.user_id,
        }

        request.post({
        url : 'https://api.sample.com/frontend/sample',
        form  : data,
        }, function (error, response, body) {
            var bodyJson = JSON.parse(body);
            console.log(bodyJson);
            res.locals.wallet = req.session.wallet; <----- HERES THE PROBLEM

            next();
        });

    } else {
        res.redirect("/login");
    }
    // next(); <----------------- remove this line
};