dbFacade.js

function db (opts) {
  const pool = new pg.Pool(config.get('pgdb'))
  
  this.query = function query (...args) {
    pool.query(...args)
  }
  
  this.withTransaction = function withTransaction (tasks, done) {
    const job = {
      client: pool,
      tasks: tasks
    }

    async.applyEachSeries([
      connect,
      beginTransaction,
      buildTransactionClient
      runTasks,
      commitTransaction
    ], job, (err, res) => {
      if (err) return rollbackTransaction(job, err, done)
      done(null, job)
    })
  }
}

function transactionClient (client) {
  this.query = function query (...args) {
    client.query(...args)
  }
  
  this.withTransaction = function withTransaction(tasks, done) {
    const job = {
      client: pool,
      tasks: tasks
    }

    runTasks(job, done)
  }
}

function buildTransactionClient (job, next) {
  job.client = new transactionClient(job.client)
  next()
}