I’m a newbie on NodeJS and I’m trying to create a layered project based on NodeJS using Typescript.
This is the folder structure I’m trying to create:

src
controllers

• user.controller.ts
  services
• user.service.ts
  routes
• user.routes.ts

index.ts

I’m trying to inject the UserService in my UserController to call a simple function, however it just won’t work.
This is the code I’m trying:

user.controller.ts

import { Request, Response } from "express";
import { UserService } from "../services/user.service";

export class UserController {
  
  private userService: UserService;
    constructor(){
      this.userService = new UserService('Hello World!');
    }
  

   getPing(_req: Request, res: Response) {
     const user = new UserService();
     const test = userService.ping();
     res.send({
       some: test,
     });
   }
}

user.service.ts

export class UserService {

  private message: string;

  constructor(message: string){
    this.message = message;
  }

  ping(): any {
    return {
      msg: `Wanna say this: ${this.message}`,
    }
  }
}

user.route.ts

import express from 'express';
import { UserController } from '../controllers/user.controller';

const router = express.Router();

const userController = new UserController();
router.get('/message', userController.getPing);

export default router;

index.ts

import express from 'express';
import userRoutes from './routes/user.routes';

const app = express();
app.use(express.json());

const PORT = 3000;

app.use('/api/users', userRoutes);

app.listen(PORT, () => {
  console.log(`Server running on port ${PORT}`);
})

As simple as that, but when I try to call the route /api/users I get the error:
TypeError: Cannot read properties of undefined (reading 'userService')

This is my package json:

{
  "name": "back",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "dev": "ts-node-dev src/index.ts",
    "tsc": "tsc",
    "start": "node build/index.js",
    "test": "echo "Error: no test specified" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@types/express": "^4.17.21",
    "ts-node-dev": "^2.0.0",
    "typescript": "^5.4.5"
  },
  "dependencies": {
    "express": "4.19.2"
  }
}

What I have already tried is to declare the userService as a const inside the controller method and it works but this I do not think this is a good practice. I want the service ready to be used by all methods in the Controller.

Please could you just direct me on how can I solve this? I’ve been struggling the whole day.