database.js

const express = require('express'),
        format = require('string-format');
let pg = undefined;

try {
    require.resolve('pg-native');
    pg = require('pg').native;
    console.log('Using pg-native');
} catch(e) {
    pg = require('pg');
    console.log('Using pg');
}

let app = express();
let database = {};

//change me to change the pool size limit
let connection_pool_limit = Math.floor(100 / 4); //default is 100 (server default as well)

let config = {
    user: '',
    database: '',
    password: "",
    host: 'localhost',
    port: 5432,
    max: 0,
    idleTimeoutMillis: 1000
};

database = {
    connect: (threads, limit = 100) => {
        if (threads) connection_pool_limit = (limit / threads);
        config.max = connection_pool_limit;
        this.pool = new pg.Pool(config);
    },

    connString: () => {
        return `postgres://${config.user}:${config.password}@${config.host}:${config.port}/${config.database}`;
    },

    getPg: (pool = false) => {
        return (pool) ? this.pool : pg;
    },

    rawQuery: (sql, params, cb) => {
        let self = this;
        if(!cb) {
            return new Promise((resolve, reject) => {
                try {
                    self.pool.connect((err, client, done) => {
                        client.query(sql, params, (err, result) => {
                            done();
                            if(err) {
                                return reject(err);
                            }
                            resolve(result);
                        });
                    });
                } catch(e) {
                    reject(e);
                }
            });
        } else {
            self.pool.connect((err, client, done) => {
                client.query(sql, params, (err, result) => {
                    done();
                    if(err){
                        return cb(false, err);
                    }
                    cb(result);
                });
            });
        }
    }
}

module.exports = (threads, limit) => {
    database.connect(threads, limit);
    return database;
};