logging.go
func GetLogger(name string) (*Logger, error) {
	if name == "default" {
		return getDefaultLogger(), nil
	}
	lock.RLock()
	logger, ok := loggers[name]
	lock.RUnlock()
	if !ok {
		return nil, fmt.Errorf("unknown logger %s", name)
	}
	return logger, nil
}
func GetLogger(name string) (*Logger, error) {
	if name == "default" {
		return getDefaultLogger(), nil
	}
	lock.RLock()
	logger, ok := loggers[name]
	lock.RUnlock()
	if !ok {
		return nil, fmt.Errorf("unknown logger %s", name)
	}
	return logger, nil
}
// GetLogger returns logger instance based on provided name.
// If logger does not exist, error will be returned.