code: func (r *Response) sendFile() {
  	log.Debugf("sending file %s", r.file)
  
  	base := filepath.Base(r.file)
  	r.writer.Header().Set("Content-Disposition", "attachment; filename="+base)
  	http.ServeFile(r.writer, r.request, r.file)
  }
docs: // Will be called from ``flush`` Response method if user called ``File`` method.