code: func (w *gzipResponseWriter) Write(b []byte) (int, error) {
  	if w.Header().Get("Content-Type") == "" {
  		w.Header().Set("Content-Type", http.DetectContentType(b))
  	}
  	if !w.statusCodeWritten {
  		w.WriteHeader(http.StatusOK)
  	}
  	n, err := w.Writer.Write(b)
  	return n, err
  }
docs: // Write wraps the underlying Write method to do compression.