api.js

var dotenv = require("dotenv").config(),
  express = require("express"),
  pg = require("pg"),
  cors = require("cors"),
  app = express();

//Allowed cors in localhost
app.use(cors());

//Database Config .env
const config = {
  user: process.env.PG_USER,
  database: process.env.PG_DATABASE,
  password: process.env.PG_PASS,
  port: process.env.PG_PORT
};

//Documentation for node-postgres: https://node-postgres.com/
const pool = new pg.Pool(config);

app.get("/api.json", (req, res, next) => {
  pool.connect(function(err, client, done) {
    if (err) {
      console.log("Can not connect to the DB because of " + err);
    }
    client.query("SELECT * FROM users", function(err, result) {
      done();
      if (err) {
        console.log(err);
        res.status(400).send(err);
      }
      res.status(200).send(result.rows);
    });
  });
});

//Server
app.listen(8080, function() {
  console.log("API listening on http://localhost:8080/api.json");
});