code: function spec(req, res) {
      if (req.uri.pathname !== specification) return;
  
      res.statusCode = 200;
      res.setHeader('Content-Type', 'application/json');
      res.end(JSON.stringify(primus.spec));
  
      return true;
    }
docs: The actual HTTP middleware.
  
  @param {Request} req HTTP request.
  @param {Response} res HTTP response.
  @api private