code: func (fw *flushWriter) Write(p []byte) (n int, err error) {
  	n, err = fw.writer.Write(p)
  	if err != nil {
  		return
  	}
  	if fw.flusher != nil {
  		fw.flusher.Flush()
  	}
  	return
  }
docs: // Write is a FlushWriter implementation of the io.Writer that sends any buffered
  // data to the client.