UnhandledPromiseRejectionWarning: Error: WHERE parameter "username" has invalid "undefined" value in postman

Currently working on a backend in nodejs for a login page. I'm following this tutorial https://bezkoder.com/node-js-jwt-authentication-mysql/

When I try to go to http://localhost:8080/api/auth/signup in postman I get these errors in my server:

set appropriate Header: Content-Type: application/json and I also set body from test to json in postman

I believe it is coming from this snippet of code, but the rest of the code is in the github link if you need more code.

Github link: https://github.com/bezkoder/node-js-jwt-auth

In verifySignup.js:

 const db = require("../models");
 const ROLES = db.ROLES;
 const User = db.user;

 checkDuplicateUsernameOrEmail = (req, res, next) => {
 // Username
User.findOne({
 where: {
   username: req.body.username
  }
  }).then(user => {
  if (user) {
   res.status(400).send({
    message: "Failed! Username is already in use!"
   });
   return;
  }

 // Email
 User.findOne({
   where: {
    email: req.body.email
   }
  }).then(user => {
   if (user) {
    res.status(400).send({
       message: "Failed! Email is already in use!"
     });
    return;
   }

   next();
 });
});
};

In auth-routes.js my request to register:

 app.post(
 '/api/auth/signup', 
 [
   verifySignUp.checkDuplicateUsernameOrEmail,
    verifySignUp.checkRolesExisted
  ],
 controller.signup
);

Server.js (all code):

const express = require("express");
const bodyParser = require("body-parser");
const cors = require("cors");

const app = express();

 var corsOptions = {
 origin: "http://localhost:8081"
};



app.use(cors(corsOptions));

// parse requests of content-type - application/json
app.use(bodyParser.json());

// parse requests of content-type - application/x-www-form-urlencoded
app.use(bodyParser.urlencoded({ extended: true }));

// routes
require('./app/routes/auth.routes')(app);
require('./app/routes/user.routes')(app);

// database
const db = require("./app/models");
const Role = db.role;

//db.sequelize.sync();
// force: true will drop the table if it already exists
db.sequelize.sync({force: true}).then(() => {
console.log('Drop and Resync Database with { force: true }');
initial();
 });

// simple route
app.get("/", (req, res) => {
res.json({ message: "Welcome to bezkoder application." });
});



// set port, listen for requests
const PORT = process.env.PORT || 8080;
app.listen(PORT, () => {
 console.log(`Server is running on port ${PORT}.`);
});

 function initial() {
 Role.create({
  id: 1,
  name: "user"
 });

 Role.create({
  id: 2,
  name: "moderator"
 });

 Role.create({
  id: 3,
  name: "admin"
 });
 }