code: func (ctxt *Context) ServeJSON(data interface{}) {
  	encoded, err := json.Marshal(data)
  	if err != nil {
  		panic(err)
  	}
  	ctxt.Header().Set("Content-Type", "application/json")
  	ctxt.Write(encoded)
  }
docs: // ServeJSON serves the request using the JSON encoding of the
  // given data. It sets the content type of the response to "application/json".