code: func (f *gzipReader) Close() error {
  	var errors []error
  	if f.ReadCloser != nil {
  		errors = append(errors, f.ReadCloser.Close())
  		f.ReadCloser = nil
  	}
  	if f.file != nil {
  		errors = append(errors, f.file.Close())
  		f.file = nil
  	}
  	return trace.NewAggregate(errors...)
  }
docs: // Close closes file and gzip writer