code: func SliceToLower(s []string) []string {
  	if s == nil {
  		return nil
  	}
  
  	l := make([]string, len(s))
  	for i, v := range s {
  		l[i] = strings.ToLower(v)
  	}
  
  	return l
  }
docs: // SliceToLower goes through the source slice and lowers all values.