@GrabConfig(systemClassLoader = true)
@Grab(group='org.postgresql', module='postgresql', version='42.1.4')

import groovy.sql.Sql

def db = [
  url: 'jdbc:postgresql://dbHost/dbName',
  user: 'user',
  password: 'pw',
  driver: 'org.postgresql.Driver'
]
Sql sql = Sql.newInstance(db.url, db.user, db.password, db.driver)

println sql.rows('SELECT * FROM schema.table');