glg.go
func (g *Glg) SetLevelWriter(level LEVEL, writer io.Writer) *Glg {
	if writer == nil {
		return g
	}

	lev, ok := g.logger.Load(level)
	if ok {
		l := lev.(*logger)
		l.writer = writer
		l.updateMode()
		g.logger.Store(level, l)
	}

	return g
}
func (g *Glg) SetLevelWriter(level LEVEL, writer io.Writer) *Glg {
	if writer == nil {
		return g
	}

	lev, ok := g.logger.Load(level)
	if ok {
		l := lev.(*logger)
		l.writer = writer
		l.updateMode()
		g.logger.Store(level, l)
	}

	return g
}
// SetLevelWriter sets writer to glg std writer per logging level