Switch to using pg.Pool

/*global require,module,process*/

var winston = require('winston');

const {Client} = require('pg');

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

// create table entries (id serial primary key, key varchar(255) not null, value text not null, expiration int, unique(key));

// A postgres document store

var PostgresDocumentStore = function (options) {

  this.expireJS = options.expire;

  this.connectionUrl = process.env.DATABASE_URL || options.connectionUrl;

  const connectionString = process.env.DATABASE_URL || options.connectionUrl;

  this.pool = new Pool({connectionString});

};

PostgresDocumentStore.prototype = {

  // A connection wrapper

  safeConnect: function (callback) {

    const client = new Client({connectionString: this.connectionUrl});

    const connectionPromise = client.connect();

    const done = () => {};

    connectionPromise.then(() => {

      callback(undefined, client, done);

    }).catch((error) => {

      console.log(error);

    this.pool.connect((err, client, done) => {

      if (err) {

        winston.error('error connecting to postgres', {error});

        callback(error);

      } else {

        callback(undefined, client, done);

      }

    });

  }

};

module.exports = PostgresDocumentStore;