src/Valkyrja/Http/NativeResponse.php
public function expire(): Response
    {
        if ($this->isFresh()) {
            $this->headers->set('Age', $this->getMaxAge());
        }

        return $this;
    }
public function expire(): Response
    {
        if ($this->isFresh()) {
            $this->headers->set('Age', $this->getMaxAge());
        }

        return $this;
    }
Marks the response stale by setting the Age header to be equal to the
maximum age of the response.

@throws \RuntimeException

@return \Valkyrja\Http\Response