logger.go
func (opt *Options) Infof(format string, v ...interface{}) {
	if opt.Logger == nil {
		return
	}
	opt.Logger.Infof(format, v...)
}
func (opt *Options) Infof(format string, v ...interface{}) {
	if opt.Logger == nil {
		return
	}
	opt.Logger.Infof(format, v...)
}
// Infof logs an INFO message to the logger specified in opts.