code: func (l *logger) Infoln(vals ...interface{}) {
  	l.mut.Lock()
  	defer l.mut.Unlock()
  	s := fmt.Sprintln(vals...)
  	l.logger.Output(2, "INFO: "+s)
  	l.callHandlers(LevelInfo, s)
  }
docs: // Infoln logs a line with an INFO prefix.