public static Executor buildExecutor() {
        GrpcRegisterConfig config = Singleton.INST.get(GrpcRegisterConfig.class);
        if (Objects.isNull(config)) {
            return null;
        }
        final String threadpool = Optional.ofNullable(config.getThreadpool()).orElse(Constants.CACHED);
        switch (threadpool) {
            case Constants.SHARED:
                try {
                    return SpringBeanUtils.getInstance().getBean(ShenyuThreadPoolExecutor.class);
                } catch (NoSuchBeanDefinitionException t) {
                    throw new ShenyuException("shared thread pool is not enable, config ${shenyu.sharedPool.enable} in your xml/yml !", t);
                }
            case Constants.FIXED:
            case Constants.EAGER:
            case Constants.LIMITED:
                throw new UnsupportedOperationException();
            case Constants.CACHED:
            default:
                return null;
        }
    }
get thread pool, just for integrated test.

@return the thread pool
shenyu-plugin/shenyu-plugin-proxy/shenyu-plugin-rpc/shenyu-plugin-grpc/src/main/java/org/apache/shenyu/plugin/grpc/client/GrpcClientBuilder.java