Github connection tester does not work through http

Hello,

I have a private repository in Github: 7system7/test. I would test my connection w/ this code:

use CzProject\GitPhp\Git;

$git = new Git();
$git->isRemoteUrlReadable('https://<username>:<token>@github.com/7system7/test.git'); // false

It always returns false, however the token has permission for everything. What have I wrong?
If I test it the same way in Gitlab or Gitea, it works.