How to set the value of loadBalancerKey in ribbon or Feign

Question

In Spring Cloud, I'm using Ribbon or Feign as the client API, and we have a server cluster registered in Eureka. In my case, I want to use the specific key to determine which server I want to call, eg: server-A has two instances, localhost:8001 and localhost:8002, and I want to call 8001 by setting the loadBalancerKey to 8001, after that I can write my customized balance rule class to choose which server I can call like below:

public class MyConfigBalanceRule extends ClientConfigEnabledRoundRobinRule {
    @Override
    public Server choose(Object key) {
        List<Server> serverList = getLoadBalancer().getAllServers();
        for (Server srv : serverList) {
            if (srv.getPort == key) {
                return srv;
            }
        }
    }
}