code: func (logger *Logger) getLineInfo(depth int) string {
  	_, f, l, ok := runtime.Caller(depth)
  	if !ok {
  		return ""
  	}
  	if f == "<autogenerated>" {
  		_, f, l, ok = runtime.Caller(depth + 1)
  		if !ok {
  			return ""
  		}
  	}
  
  	base := path.Base(f)
  	dir := path.Dir(f)
  	folders := strings.Split(dir, "/")
  	parent := ""
  	if folders != nil {
  		parent = folders[len(folders)-1] + "/"
  	}
  	file := parent + base
  	line := strconv.Itoa(l)
  	return fmt.Sprintf("%s(%s)", file, line)
  }
docs: // getLineInfo returns the location (filename + linenumber) of the caller.