private SharedResourceHolder.Resource<Executor> wrapExecutor(final Executor executor) {
        return new SharedResourceHolder.Resource<Executor>() {
            @Override
            public Executor create() {
                return executor;
            }

            @Override
            public void close(Executor instance) {
//                instance.shutdown();
                // ignore
            }

            @Override
            public String toString() {
                return name;
            }
        };
    }
copy from : https://github.com/grpc/grpc-java/blob/master/core/src/main/java/io/grpc/internal/DnsNameResolverProvider.java
grpc/src/main/java/io/grpc/internal/PinpointDnsNameResolverProvider.java