use Symfony\Component\Cache\Adapter\FilesystemAdapter;
use Symfony\Component\Cache\Psr16Cache;
// the PSR-6 cache object that you want to use
$psr6Cache = new FilesystemAdapter();
// a PSR-16 cache that uses your cache internally!
$psr16Cache = new Psr6Cache($psr6Cache); # <--- Wrong?
$psr16Cache = new Psr16Cache($psr6Cache); # <--- Correct?
// now use this wherever you want
$githubApiClient = new GitHubApiClient($psr16Cache);