由于io.ReadCloser读完后,只剩下EOF标记, 如果想再次读取的话,需要再重新给Request.body赋值.

bodyBytes, _ := ioutil.ReadAll(req.Body)
req.Body = ioutil.NopCloser(bytes.NewBuffer(bodyBytes))
// use bodyBytes
// pass to next middleware

参考

1. https://stackoverflow.com/questions/46948050/how-to-read-request-body-twice-in-golang-middleware