code: func (logger *Logger) SetTag(tag ...string) {
  	goID := logger.curGoroutineID()
  	var t string
  	if len(tag) > 0 {
  		t = tag[0]
  	} else {
  		id, err := uuid.NewV4()
  		if err != nil {
  			panic(fmt.Errorf("error generating uuid: " + err.Error()))
  		}
  		t = id.String()[0:8]
  	}
  	logger.tagMap.Store(goID, t)
  }
docs: // SetTag allows to define a string tag for the current go routine. Otherwise
  // numeric identification is used.