index.js

const express = require('express')
const { Pool } = require('pg')

const app = express()
const port = 3000

let connection = {
  host: 'localhost',
  port: 5432,
  database: 'postgres',
  user: 'postgres',
  password: 'postgres'
}

if (process.env.DATABASE_URL) {
  connection = { connectionString: process.env.DATABASE_URL }
}

const db = new Pool(connection)

app.get('/', async (_, response) => {
  const { rows } = await db.query('SELECT NOW();')
  response.send(`<h1>The current database time is ${rows[0].now}</h1>`)
})

app.listen(port, () => console.log(`Server on at http://localhost:${port}`))