code: func (d Data) BindJSON(v interface{}) error {
  	if len(d.jsonBody) == 0 {
  		return nil
  	}
  	return json.Unmarshal(d.jsonBody, v)
  }
docs: // BindJSON binds v to the json data in the request body. It calls json.Unmarshal and
  // sets the value of v.