code: func (r *Response) Json(obj interface{}) error {
  	res, err := json.Marshal(obj)
  	if err != nil {
  		return err
  	}
  
  	r.writer.Header().Set("Content-Type", "application/json")
  	return r.Raw(res)
  }
docs: ///////////////////////////////////////////////////////////////////
  // Creating Responses
  ///////////////////////////////////////////////////////////////////
  // Will produce JSON string representation of passed object,
  // and send it to client