code: func NewMultiWriteCloser(writeClosers ...io.WriteCloser) io.WriteCloser {
  	writers := make([]io.Writer, len(writeClosers))
  	for i, w := range writeClosers {
  		writers[i] = w
  	}
  	return multiWriteCloser{Writer: io.MultiWriter(writers...), closers: writeClosers}
  }
docs: // NewMultiWriteCloser creates a new io.WriteCloser that duplicates its writes to all the
  // provided writers.