log/logger.go
func (l Level) String() string {
	switch l {
	case LevelTrace:
		return "trace"
	case LevelDebug:
		return "debug"
	case LevelInfo:
		return "info"
	case LevelWarn:
		return "warn"
	case LevelError:
		return "error"
	case LevelFatal:
		return "fatal"
	}
	// return default info
	return "info"
}
func (l Level) String() string {
	switch l {
	case LevelTrace:
		return "trace"
	case LevelDebug:
		return "debug"
	case LevelInfo:
		return "info"
	case LevelWarn:
		return "warn"
	case LevelError:
		return "error"
	case LevelFatal:
		return "fatal"
	}
	// return default info
	return "info"
}
// String returns level String