Post request pending on MERN-CodePudding

I'm trying to learn the MERN stack. I'm creating my first very simple site. Now, I created a route where I create an user, using the datas passed throw body. Here is the code of the server:

const express = require('express');
const cors = require('cors');
const mongoose = require('mongoose');

require('dotenv').config();


const app = express();
const port = process.env.PORT || 5000;

app.use(cors);
app.use(express.json());

const uri = process.env.ATLAS_URI;
mongoose.connect(uri, { useNewUrlParser:true });

const connection = mongoose.connection;
connection.once('open', () =>{
    console.log("MongoDB database connection established succesfully")
})

const usersRouter = require('./routes/users');
app.use('/users', usersRouter); 

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

Now, here is the code of the users router file, into i put the code:

const router = require('express').Router();//setting it as a express router
let User = require('../models/user.model');//requise the model created before

router.route('/').get((req, res) => {
  User.find()//mongoose method, returns a promise
    .then(users => res.json(users))//return the list of user
    .catch(err => res.status(400).json('Error: '   err));
});

router.route('/add').post((req, res) => {
  const username = req.body.username;

  const newUser = new User({username});

  newUser.save()
    .then(() => res.json('User added!'))
    .catch(err => res.status(400).json('Error: '   err));
});

module.exports = router;

And, in the end, here is the model user schema:

const mongoose = require('mongoose');

const Schema = mongoose.Schema;


//create the schema for the user
//like the model in Flask
const userSchema = new Schema({
    username: {
        type: String,
        required: true,
        unique: true,
        trim: true,
        minlength: 3
    },
},{
    timestamps:true,
});

const User = mongoose.model('User', userSchema); //create the model, via the schema

module.exports = User;

Now, to test if it is correct, before implement other code and the frontend, I would like to test it out. First I would like to add a new user, to see if the API works properly. I'm using postman. I sent the request on this URL: http://127.0.0.1:5000/users/add, with the following json in the body:{"username": "name"}. Then I send, but Postman continue to say me that it is sending the request, and it continues for minutes. I can't understand if the problem is the promise, that is too low, if I wrote something incorrectly in the code or in the test configuration, if there are issues with the Mongo database, or anything else. Can you help me please? Thanks

CodePudding user response：

in your DB connection you are not waiting for the promise to be resolved

    require('dotenv').config();
    const express = require('express');
    const cors = require('cors');
    const mongoose = require('mongoose');
    
    const app = express();
    app.use(cors());
    app.use(express.json());
    
    const port = process.env.PORT || 5000;
    
    const connectDB = async () => {
      try {
        const conn = await mongoose.connect(process.env.ATLAS_URI, {
          useUnifiedTopology: true,
          useNewUrlParser: true,
        });
    
        console.log(`MongoDB Connected: ${conn.connection.host}`);
      } catch (err) {
        console.error(`Error: ${err.message}`);
        process.exit(1);
      }
    };
    
    
    connectDB()
    
    
    const usersRouter = require('./routes/users');
    app.use('/users', usersRouter); 
    
    app.listen(port, () => {
        console.log(`Server is running on port: ${port}`);
    });