controller_user.js

const makeValidation = require('@withvoid/make-validation');
const  UserModel = require('../models/user.js');
const  {USER_TYPES}  = UserModel;

module.exports = {
  onGetAllUsers: async (req, res) => {
    try {
      const users = await UserModel.getUsers();
      return res.status(200).json({ success: true, users });
    } catch (error) {
      return res.status(500).json({ success: false, error: error })
    }
    
  },
  onGetUserById: async (req, res) => {
    try {
      const user = await UserModel.getUserById(req.params.id);
      return res.status(200).json({ success: true, user });
    } catch (error) {
      return res.status(500).json({ success: false, error: error })
    }
  },
  onCreateUser: async (req, res) => {
    try {
      const validation = makeValidation(types =>({
        payload: req.body,
        checks: {
          firstName: { type: types.string },
          lastName: { type: types.string },
          type: { type: types.enum, 
            options: { enum: USER_TYPES } },
        }
        }));

        if (!validation.success) return res.status(400).json(validation);
      const { firstName, lastName, type } = req.body;
      const user = await UserModel.createUser(firstName, lastName, type);
      console.log('test3');
      return res.status(200).json({ success: true, user });
    } catch (error) {
      console.log(error);
      return res.status(500).json({ success: false, error: error })
    }
  },
  onDeleteUserById: async (req, res) => {
    try {
      const user = await UserModel.deleteByUserById(req.params.id);
      return res.status(200).json({
        success: true,
        message: `Deleted a count of ${user.deletedCount} user.`
      });
    } catch (error) {
      return res.status(500).json({ success: false, error: error })
    }
  },
};

error o n visual studio

Mongo has connected successfully
POST /users 500 524.686 ms - 28
[nodemon] restarting due to changes...
[nodemon] starting `node server/index.js`
Listening on port :: http:/localhost:3000/
Mongo has connected successfully
TypeError: UserModel.createUser is not a function
    at onCreateUser (C:\Users\SAMUEL\Documents\codes\chatapp\chatapp\controllers\user.js:37:36)
    at Layer.handle [as handle_request] (C:\Users\SAMUEL\Documents\codes\chatapp\chatapp\node_modules\express\lib\router\layer.js:95:5)
    at next (C:\Users\SAMUEL\Documents\codes\chatapp\chatapp\node_modules\express\lib\router\route.js:137:13)
    at Route.dispatch (C:\Users\SAMUEL\Documents\codes\chatapp\chatapp\node_modules\express\lib\router\route.js:112:3)
    at Layer.handle [as handle_request] (C:\Users\SAMUEL\Documents\codes\chatapp\chatapp\node_modules\express\lib\router\layer.js:95:5)
    at C:\Users\SAMUEL\Documents\codes\chatapp\chatapp\node_modules\express\lib\router\index.js:281:22
    at Function.process_params (C:\Users\SAMUEL\Documents\codes\chatapp\chatapp\node_modules\express\lib\router\index.js:335:12)
    at next (C:\Users\SAMUEL\Documents\codes\chatapp\chatapp\node_modules\express\lib\router\index.js:275:10)
    at Function.handle (C:\Users\SAMUEL\Documents\codes\chatapp\chatapp\node_modules\express\lib\router\index.js:174:3)
    at router (C:\Users\SAMUEL\Documents\codes\chatapp\chatapp\node_modules\express\lib\router\index.js:47:12)
    at Layer.handle [as handle_request] (C:\Users\SAMUEL\Documents\codes\chatapp\chatapp\node_modules\express\lib\router\layer.js:95:5)
    at trim_prefix (C:\Users\SAMUEL\Documents\codes\chatapp\chatapp\node_modules\express\lib\router\index.js:317:13)
    at C:\Users\SAMUEL\Documents\codes\chatapp\chatapp\node_modules\express\lib\router\index.js:284:7
    at Function.process_params (C:\Users\SAMUEL\Documents\codes\chatapp\chatapp\node_modules\express\lib\router\index.js:335:12)
    at next (C:\Users\SAMUEL\Documents\codes\chatapp\chatapp\node_modules\express\lib\router\index.js:275:10)
    at urlencodedParser (C:\Users\SAMUEL\Documents\codes\chatapp\chatapp\node_modules\body-parser\lib\types\urlencoded.js:82:7)
POST /users 500 334.781 ms - 28

index.js

const config = {
    db:{
        url: 'localhost:27017',
        name: 'chatdb'
    }
}

export default config


/// i am having a bug with line 8
/* export default config
^^^^^^

SyntaxError: Unexpected token export */

model_user.js

const mongoose = require('mongoose');
const { v4 : uuidv4} = require('uuid');

const USER_TYPES = {
    CONSUMER: "consumer",
    SUPPORT: "support"
};
const userSchema = new mongoose.Schema(
    
    {
        _id:{
            type: String , 
            default: () => uuidv4().replace(/\-/g, ""),
        },
        firstName: String, 
        lastName: String,
        type:String, 
    },
    {
        timestamps:true,
        collection: "users",
    }
);

userSchema.statics.createUser = async function (firstName,lastName,type) {
    return this.create({ firstName, lastName, type });
}
userSchema.statics.getUserById = async function (id) {
    try {
        const user = await this.findOne({ _id: id });
        if (!user) throw ({ error: 'No user with this id found' });
        return user;
    } catch (error) {
        throw error;
    }
}
userSchema.statics.getUsers = async function () {
    try {
        const users = await this.find();
        return users;
    } catch (error) {
        throw error;
    }
}
userSchema.statics.deleteByUserById = async function (id) {
    try {
        const result = await this.remove({ _id: id });
        return result;
    } catch (error) {
        throw error;
    }
}
const usermodel = mongoose.model("User", userSchema);

module.exports = {
    usermodel,
    USER_TYPES
}

mongo.js

const mongoose = require('mongoose');
const config = require('../config/index.js');

const CONNECTION_URL = `mongodb://${config.db.url}/${config.db.name}`

mongoose.connect(CONNECTION_URL, {
    useNewUrlParser:true,
    useUnifiedTopology: true
})

mongoose.connection.on('connected', () => {
    console.log ('Mongo has connected successfully');

})
mongoose.connection.on('reconnected', () => {
    console.log('Mongo has reconnected')
})
mongoose.connection.on('error', error => {
    console.log('Mongo connection has an error', error)
    mongoose.disconnect()
})
mongoose.connection.on('disconnected', () => {
    console.log('Mongo connection is disconnected')
})

route_user.js

const express = require('express');

const router = express.Router();


//controllers
const user = require('../controllers/user.js');

router
    .get('/', user.onGetAllUsers)
    .post('/', user.onCreateUser)
    .get('/:id', user.onGetUserById)
    .delete('/:id', user.onDeleteUserById)


module.exports = router;

routes_index.js

const express = require('express');
const users = require('../controlllers/user.js');

const { encode } = require('../middlewares/jwt.js');

const router = express.Router();

router 
    .post('/login/:userId', encode, (req, res, next) => { });

module.exports = router;

The syntax you're using on line 8 only works when using ES Modules or a transpiler such as Babel with the import plugin. There are a couple of ways to solve this. The easiest is to just use module.exports. module isn't global, but local to the module where it's being defined.

module.exports = config on line 8 should solve your issue.

For more information on the nuance between them, this is a terse but solid reference: https://adrianmejia.com/getting-started-with-node-js-modules-require-exports-imports-npm-and-beyond/

Okay thanks for link i will check it out ......i have updated the files