Decoding gZip json with Go - json

Question

As a Go newbie it's difficult for me to pinpoint the problem area, but hopefully giving you some facts will help.
I'm playing with an API which returns its Content-Encoding as gzip. I have written the following to encode my response struct:
reader, err = gzip.NewReader(resp.Body)
defer reader.Close()
// print to standard out
//_, err = io.Copy(os.Stdout, reader)
//if err != nil {
// log.Fatal(err)
//}
// Decode the response into our tescoResponse struct
var response TescoResponse
err := json.NewDecoder(reader).Decode(&response)
I've removed the error handling for brevity, but the point of interest is that if I uncomment the print to stdout, I get the expected result. However, the decode doesn't give me what I expect. Any pointers? Is it that the struct has to map exactly to the response??
Here's the full example:
https://play.golang.org/p/4eCuXxXm3T

Answer 1

From the documenation:
DisableCompression, if true, prevents the Transport from requesting
compression with an "Accept-Encoding: gzip" request header when the
Request contains no existing Accept-Encoding value. If the Transport
requests gzip on its own and gets a gzipped response, it's
transparently decoded in the Response.Body. However, if the user
explicitly requested gzip it is not automatically uncompressed.
Proposed solution:
type gzreadCloser struct {
*gzip.Reader
io.Closer
}
func (gz gzreadCloser) Close() error {
return gz.Closer.Close()
}
// then in your http call ....
if resp.Header.Get("Content-Encoding") == "gzip" {
resp.Header.Del("Content-Length")
zr, err := gzip.NewReader(resp.Body)
if err != nil {
return nil, err
}
resp.Body = gzreadCloser{zr, resp.Body}
}
// then you will be able to decode the json transparently
if err := json.NewDecoder(resp.Body).Decode(&response); err != nil {
}
Adapted solution from your code: https://play.golang.org/p/Vt07y_xgak

Answer 2

As #icza mentioned in the comments, decoding isn't required because the gzip reader automatically decodes when you read using it. Perhaps try:
ubs := make([]byte, len) // check Content-Length header to set len
n, err := reader.Read(ubs)
err := json.Unmarshal(ubs, &response)