code: func NewStreamArachive(w io.Writer) *StreamArchive {
  	s := &StreamArchive{}
  	s.gw = gzip.NewWriter(w)
  	s.Writer = tar.NewWriter(s.gw)
  	return s
  }
docs: // NewStreamArachive returns a new streamable archive with given io.Writer.
  // It's caller's responsibility to close io.Writer and streamer after operation.