Describe the bug

When searching for 'containers/auth.json', in go-containerregistry/pkg/authn/keychain.go, the environment variable XDG_RUNTIME_DIR should be replaced with XDG_CONFIG_HOME and if missing with $HOME/.config.

See: https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html

So
f, err := os.Open(filepath.Join(os.Getenv("XDG_RUNTIME_DIR"), "containers/auth.json"))

Should be
f, err := os.Open(filepath.Join(os.Getenv("XDG_CONFIG_HOME"), "containers/auth.json"))
and
f, err := os.Open(filepath.Join(os.Getenv("HOME"), ".config/containers/auth.json"))