@Override
    public synchronized void shutdown() {
        if (this.cliClientService == null) {
            return;
        }
        this.cliClientService.shutdown();
        this.cliClientService = null;
    }
Cli service implementation.

@author boyan (boyan@alibaba-inc.com)
@author jiachun.fjc
jraft-core/src/main/java/com/alipay/sofa/jraft/core/CliServiceImpl.java