code: func (t *Torrent) newMetaInfo() metainfo.MetaInfo {
  	return metainfo.MetaInfo{
  		CreationDate: time.Now().Unix(),
  		Comment:      "dynamic metainfo from client",
  		CreatedBy:    "go.torrent",
  		AnnounceList: t.metainfo.UpvertedAnnounceList(),
  		InfoBytes: func() []byte {
  			if t.haveInfo() {
  				return t.metadataBytes
  			} else {
  				return nil
  			}
  		}(),
  	}
  }
docs: // Returns a run-time generated MetaInfo that includes the info bytes and
  // announce-list as currently known to the client.