code: func (e *LoggingErrorGroup) Add(err error) {
  	e.total++
  	if err != nil {
  		LogMethod("%s: %s", e.name, err)
  		e.failed++
  	}
  }
docs: // Add will handle a given error. If the error is non-nil, total and failed
  // are both incremented and the error is logged. If the error is nil, only
  // total is incremented.