glg.go
func (g *Glg) CustomLogf(level string, format string, val ...interface{}) error {
	return g.out(g.TagStringToLevel(level), format, val...)
}
func (g *Glg) CustomLogf(level string, format string, val ...interface{}) error {
	return g.out(g.TagStringToLevel(level), format, val...)
}
// CustomLogf outputs formatted custom level log