func responseBodyDecoder(resp http.Response,response interface{}) {
    // get result form Response
    decoder := json.NewDecoder(resp.Body)
    decode_err := decoder.Decode(response)
    if decode_err != nil {
        panic(decode_err)
    }
}

ret:=loginResult{}
responseBodyDecoder(resp, &ret)

ret2:=responseResult{}
responseBodyDecoder(resp, &ret2)

type responseResult struct {
    Result string
}