get and use connection string from env

config.js

module.exports = {
	jwt: env('JWT_SECRET'),
	pg: {
		connection: `postgres://app:${env('PG_APP_PWD', 'app')}@${env('PG_HOST', 'localhost')}/db`,
		client: 'pg',
	},
	pgTwo: {
		connection: `postgres://app2:${env('PG_APP2_PWD', 'APP2')}@${env('PG_APP2_HOST', 'localhost:port')}/db2`,
		client: 'pg',
	},
	queue: `amqp://app:${env('RMQ_APP_PWD', 'app')}@${env('RMQ_HOST', 'localhost')}/app`,
}

function env (key, defaultValue) {
	const value = process.env[key] || defaultValue
	if (!value) {
		throw new Error(`process.env.${key} is missing!`)
	}
	return value
}

pg.js

const config = require('./config')
const knex = require('knex')(config.pg)
module.exports = knex

updateUser.js

const pg = require('./pg')

const getUserUpdateAt = pg('Users')
  .where({ id: user.id })
  .first()
  .then(it => _.get(it,'updated_at'))

//continue...