private function setAppNamespace($oldNamespace, $newNamespace)
    {
        $files = $this->filesystem->files(app_path());

        foreach ($files as $file) {
            $content = $this->filesystem->get($file);
            $this->filesystem->create($file, preg_replace("/\\b" . $oldNamespace . "\\b/", $newNamespace, $content));
        }
    }