public function createConnection($dsn, array $config, array $options)
{
    $username = Arr::get($config, 'username');

    $password = Arr::get($config, 'password');

    try {
        $pdo = new PDO($dsn, $username, $password, $options); // <== THIS ONE
    } catch (Exception $e) {
        $pdo = $this->tryAgainIfCausedByLostConnection(
            $e, $dsn, $username, $password, $options
        );
    }

        return $pdo;
    }

DB_HOST=myapp-cluster.cluster-123abc.eu-west-2.rds.amazonaws.com
DB_HOST_WRITE=myapp-cluster.cluster-123abc.eu-west-2.rds.amazonaws.com
DB_HOST_READ=myapp-cluster.cluster-ro-123abc.eu-west-2.rds.amazonaws.com