http：ContentLength = 99，正文长度为0

I have this function to execute http request

func do(r *http.Request) (response *http.Response, e error) {
    r.Header.Set(SessionHeader, client.SessionId)
    response, e = client.Do(r)
    if e != nil {
        return nil, e
    }
    if response.StatusCode == http.StatusConflict {
        client.SessionId = response.Header.Get(SessionHeader)
        r.Header.Set(SessionHeader, client.SessionId)
        response, e = client.Do(r)
        if e != nil {
            return nil, e
        }
        return
    } else if response.StatusCode != http.StatusOK {
        return nil, errors.New("status Not OK")
    }
    return
}

So I make a request, than if my session id is not valid, I set header from response and try again. The issue is that the Body got flushed when I do this and this error pops up:

Post http://localhost/api: http: ContentLength=99 with Body length 0

How can I workaround this problem?

Create a request and use it.

func do(r *http.Request) (response *http.Response, err error) {
    r.Header.Set(SessionHeader, client.SessionId)
    response, err = client.Do(r)
    if err != nil {
        return nil, err
    }

    if response.StatusCode == http.StatusConflict {
        // Get SessionId
        client.SessionId = response.Header.Get(SessionHeader)

        // Create Request
        req, err := http.NewRequest("GET", "http://example.com", nil)   
        req.Header.Set("SessionHeader", client.SessionId)

        response, err := client.Do(req)
        if err != nil {
            return nil, err
        }
        return
    } else if response.StatusCode != http.StatusOK {
        return nil, errors.New("status Not OK")
    }
    return
}