code: func repl(match string, t time.Time) string {
  	if match == "%%" {
  		return "%"
  	}
  
  	formatFunc, ok := formats[match]
  	if ok {
  		return formatFunc(t)
  	}
  	return formatNanoForMatch(match, t)
  }
docs: // repl replaces % directives with right time