public static Configuration getInstance() {
        if (conf == null) {
            synchronized (Configuration.class) {
                if (conf == null) {
                    conf = new Configuration();
                }
            }
        }
        return conf;
    }
singleton for configuration.

@return static instance of Configuration
inlong-audit/audit-service/src/main/java/org/apache/inlong/audit/service/config/Configuration.java