var connection = mysql.createConnection({
  host     : 'localhost',
  user     : 'dbuser',
  password : 's3kreee7',
  database : 'my_db'
});

var connection = mysql.createConnection({
    host: process.env.RDS_HOSTNAME,
    user: process.env.RDS_USERNAME,
    password: process.env.RDS_PASSWORD,
    port: process.env.RDS_PORT
});

host: process.env.RDS_HOSTNAME || hostVariablePulledFromLocalFile