code: func (f *gzipWriter) Close() error {
  	var errors []error
  	if f.Writer != nil {
  		errors = append(errors, f.Writer.Close())
  		f.Writer.Reset(ioutil.Discard)
  		writerPool.Put(f.Writer)
  		f.Writer = nil
  	}
  	if f.file != nil {
  		errors = append(errors, f.file.Close())
  		f.file = nil
  	}
  	return trace.NewAggregate(errors...)
  }
docs: // Close closes gzip writer and file