gzip.go

	url := fmt.Sprintf("%v/dist/v1/%v/artifact/%v/%v", baseURL, repoName, version, runtime.GOOS)
	debug("GET", url)
	resp, err := client.Get(url)
	if err != nil {
		return errors.Wrap(err, "could not request latest version download")
	}
	defer resp.Body.Close()
	debug("GET", resp.StatusCode, url)
	if !(200 <= resp.StatusCode && resp.StatusCode < 300) {
		data, _ := ioutil.ReadAll(resp.Body)
		return errors.Errorf("invalid status code %v: %v", resp.StatusCode, string(data))
	}

	decompressed, err := gzip.NewReader(resp.Body)
	if err != nil {
		return errors.Wrap(err, "could not decode gzip header")
	}

	tarArchive := tar.NewReader(decompressed)
	binaryName := fmt.Sprintf("%v-%v.%v-amd64/aton", repoName, version, runtime.GOOS)
	debug("looking for", binaryName, "in archive")

	for {
		hdr, err := tarArchive.Next()
		if err != nil && err == io.EOF {
			break
		} else if err != nil {
			return errors.Wrap(err, "could not decode response")
		}
		debug("found", hdr.Name)
		if hdr.Name != binaryName {
			continue
		}

		_, err = io.Copy(target, tarArchive)
		if err != nil {
			return errors.Wrap(err, "could not copy response into file")
		}
		return nil
	}

	return errors.Errorf("could not find %v in archive", binaryName)