golang 修改 http request body

buffer, _ := ioutil.ReadAll(c.Request.Body)
c.Request.Body = ioutil.NopCloser(bytes.NewBuffer(buffer))
formValues := url.Values{}
formValues.Set("first", "1")
formValues.Set("second", "2")
formDataStr := formValues.Encode()
formDataBytes := []byte(formDataStr)
buffer = append(buffer, formDataBytes...)
c.Request.ContentLength = int64(len(buffer))
c.Request.Body = ioutil.NopCloser(bytes.NewBuffer(buffer))

协议使用 form-unlencoded