code: func PrintHeader(w io.Writer, columns ...string) {
  	underline := make([]string, len(columns))
  	for i := range underline {
  		underline[i] = strings.Repeat("-", len(columns[i]))
  	}
  	fmt.Fprintf(w, "%s\n", strings.Join(columns, "\t"))
  	fmt.Fprintf(w, "%s\n", strings.Join(underline, "\t"))
  }
docs: // PrintHeader prints a nice little header.