engine = create_engine('postgresql://postgres:passw0rd@localhost:5432/mini_amazon')
    Session = sessionmaker(bind=engine, expire_on_commit=False)

    @contextmanager
    def session_scope():
        """
        Provide a transactional scope around a series of operations.
        """
        session = Session()
        try:
            yield session
            session.commit()
        except:
            session.rollback()
            raise
        finally:
            session.close()

    with session_scope() as session:
        while True:
            print('Waiting')
            order = session.query(models.Order).get(arrived_message.packageid)
            time.sleep(1)
            if order.status == 'packed':
                break

        order.status = 'loading'