Node.js передает переменную / объект из одного модуля и возвращает его

//databaseLoginUser.js

var express = require('express');
var router = express.Router();
var mysql = require('mysql');

module.exports.getModuleFunction = function(userName, callback) {
  queryUser(userName);

  function queryUser(userName) {
    console.log('In Query User; ');
    var database = mysql.createConnection({
      host: "xxx.xxx.xxx.xxx",
      port: "3306",
      user: "UserName",
      password: "Password",
      database: "Students",
      multipleStatements: true
    });

    database.connect();

    console.log('test');

    database.query('SELECT StudentUsername, StudentPassword FROM STUDENT WHERE StudentUsername = ?', userName, function(err, rows, fields) {
      if (err) {
        console.log(err);
      }
      //console.log(rows);
      console.log('Database Returned User: ' + rows[0].StudentUsername);
      console.log('Database Returned Password: ' + rows[0].StudentPassword);
      var hashFromDatabaseBuffer = Buffer.from(rows[0].StudentPassword);
      returnPassHash(hashFromDatabaseBuffer);
      return returnPassHash;
    })

    function returnPassHash(hashFromDatabaseBuffer) {
      console.log('Do I get here?; ');
      return hashFromDatabaseBuffer;
    }
  }
};

//loginUser.js
var express = require('express');
var router = express.Router();
var mysql = require('mysql');
var bodyParser = require('body-parser');
var async = require('async');
var app = express();
var expressValidator = require('express-validator');
var securePassword = require('secure-password');
var database = require('./db');
var queryPass = require('./databaseLoginUser');

router.get('/', function(req, res, next) {
  'use strict';
  console.log('in the login user get route');
  res.render('signUp');
});

router.post('/', function(req, res, next) {
  'use strict';
  console.log('in Login Route');
  var userName = req.body.userName;
  var preHashPass = req.body.password;

  queryPass.getModuleFunction(userName, function(data) {
    passHash('', '', data)
  });

  function passHash(userName, preHashPass, hashFromDatabaseBuffer) {
    // Initialise our password policy
    var pwd = securePassword()
    var postPassHash = Buffer.from(preHashPass);

    // Register user
    pwd.hash(postPassHash, function(err, hash) {
      if (err) throw err
      // Save hash somewhere
      console.log('Form Password Hashed:');
      console.log(hash);

      pwd.verify(postPassHash, hashFromDatabaseBuffer, function(err, result) {
        console.log('Verify Result: ');
        console.log(result);
        if (err) throw err
        if (result === securePassword.INVALID) {
          return res.render('index');
          return console.log('Imma call the cops')
          res.render('index');
        } else {
          if (result === securePassword.INVALID_UNRECOGNIZED_HASH) return console.error('This hash was not made with secure-password. Attempt legacy algorithm')
          if (result === securePassword.VALID) console.log('Yay you made it')
          if (result === securePassword.VALID_NEEDS_REHASH) {
            console.log('Yay you made it, wait for us to improve your safety')

            pwd.hash(hashFromDatabase, function(err, improvedHash) {
              if (err) console.error('You are authenticated, but we could not improve your safety this time around')

              // Save improvedHash somewhere
              hash = improvedHash;
            })
          }

          var verifiedHash = hash;
          console.log('verifiedHash: ');
          console.log(verifiedHash);

          //Give User Auth Token Here
          console.log('You Get an auth Token: ');
          res.render('studentDash');
        }

      }) // pwd.verify


    });
    pwd.hash
  }; // pass hash
})

module.exports = router;