let pg = require('pg-then');

let pool = pg.Pool('postgres://username:password@localhost/database');

pool.query('SELECT ...')
.then(...)
.catch(...);

let pg = require('pg-then');

let client = pg.Client('postgres://username:password@localhost/database');

client.query('SELECT ...')
.then(...)
.catch(...);

// ...

client.end();