public function env(string $key)
    {
        $result = null;
        $break  = false;
        $keys   = explode('.', $key);
        $env    = $this->config->env;
        foreach ($keys as $key) {
            if (isset($env[$key])) {
                $env = $env[$key];
            } else {
                $break = true;
                break;
            }
        }
        if (!$break) {
            $result = $env;
        }
        return $result;
    }