code: func (b *Bmatrix) handleUploadFiles(msg *config.Message, channel string) (string, error) {
  	for _, f := range msg.Extra["file"] {
  		if fi, ok := f.(config.FileInfo); ok {
  			b.handleUploadFile(msg, channel, &fi)
  		}
  	}
  	return "", nil
  }
docs: // handleUploadFiles handles native upload of files.