code: func (p *printer) fw(minWidth int, format string, args ...interface{}) {
  	s := fmt.Sprintf(format, args...)
  	pad := minWidth - utf8.RuneCountInString(s)
  	if pad < 1 {
  		pad = 1
  	}
  	p.f("%s%s", s, strings.Repeat(" ", pad))
  }
docs: // fw is like f, but appends whitespace such that the printed string takes at
  // least minWidth.
  // Appends at least one space.