Inside: func (s *RepositoriesService) GetArchiveLink(ctx context.Context, owner, repo string, archiveformat ArchiveFormat, opts *RepositoryContentGetOptions, maxRedirects int) (*url.URL, *Response, error), it checks for an HTTP code 302:

if resp.StatusCode != http.StatusFound {
    return nil, newResponse(resp), fmt.Errorf("unexpected status code: %s", resp.Status)
}

When testing with curl, it seems the curl calls returns 200 when they are an installation, rather than 302.