code: func (wp *WriterPool) Get(w io.Writer, size int) *bufio.Writer {
  	v, n := wp.pool.Get(size)
  	if v != nil {
  		bw := v.(*bufio.Writer)
  		bw.Reset(w)
  		return bw
  	}
  	return bufio.NewWriterSize(w, n)
  }
docs: // Get returns bufio.Writer whose buffer has at least size bytes.