rpc_module.rs

					std::thread::sleep(std::time::Duration::from_millis(500));
				});
				Ok(())
			})
			.unwrap();

		let mut my_sub: TestSubscription = module.test_subscription("my_sub", Vec::<()>::new()).await;
		let (val, id) = my_sub.next::<String>().await.unwrap();
		assert_eq!(&val, "lo");
		assert_eq!(id, v2::params::SubscriptionId::Num(my_sub.subscription_id()));

		// close the subscription to ensure it doesn't return any items.
		my_sub.close();
		assert_eq!(None, my_sub.next::<String>().await);
	}
}