Unexpected behavior: Closing body stream result in an error

[Nek-]

This issue is a follow up on a discussion that occurs on telegram: @trowski specified it should be an issue, so I open one!

It's related to the discussion I already opened here: #363

Using this code:

$this->response->getBody()->close();

Results in an error like the following:

PHP Fatal error:  Uncaught Amp\Pipeline\DisposedException: The iterator has been disposed in vendor/amphp/pipeline/src/Internal/QueueState.php:185

Instead, a cancellation exception is expected.