@Override
    public void shutdown() {
        if (!this.started.compareAndSet(true, false)) {
            return;
        }
        ExecutorServiceHelper.shutdownAndAwaitTermination(this.defaultExecutor);
        GrpcServerHelper.shutdownAndAwaitTermination(this.server);
    }
GRPC RPC server implement.

@author nicholas.jxf
@author jiachun.fjc
jraft-extension/rpc-grpc-impl/src/main/java/com/alipay/sofa/jraft/rpc/impl/GrpcServer.java