当json.NewDecoder.Decode失败时，如何保存响应正文？

Question

This gist of this snippet seems to be fairly common in Go:

if err := json.NewDecoder(r.Body).Decode(&mr); err != nil {
    return mr, err
}

But how do I actually retrieve a string representation of r.Body in event of an error? In this case, it would be advantageous to include this with the error log as opposed to working through the struct only to find that Zip is sometimes a string and sometimes an integer.

Unfortunately, the body has already been closed at this point, so I'm not sure how to access it again.

Preemptively decoding the body to a string, and then later encoding it and attempting the struct mapping seems like an extra step. Is there a better way?

Answer 1

If you want to save the body, then save the body before Unmarshalling.

//...
body, err := ioutil.ReadAll(r.Body)
if err != nil {
    return err
}

err = json.Unmarshal(body, &mr)
//...