code: func (pool *DeflatePool) GetWriter(dst io.Writer) (writer *flate.Writer) {
  	if w := pool.pool.Get(); w != nil {
  		writer = w.(*flate.Writer)
  		writer.Reset(dst)
  	} else {
  		writer, _ = flate.NewWriter(dst, flate.BestCompression)
  	}
  	return writer
  }
docs: // GetWriter returns flate.Writer from the pool, or creates a new one
  // with flate.BestCompression if the pool is empty.