Get wrong instance list at first time
How to reproduce this issue, refer to followings:

    I have registered 2 instances (ex service name are all 'a') to nacos server
    Then I stop them
    After a while, I do step 1 again
    Then I get 2 instances from interface, for first time, it returns 1 instance or 0 instance. But I invoke again, it is fine to return 2 instances. Guess the cache issue?
diff --git a/spring-cloud-alibaba-nacos-discovery/src/main/java/org/springframework/cloud/alibaba/nacos/ribbon/NacosServerList.java b/spring-cloud-alibaba-nacos-discovery/src/main/java/org/springframework/cloud/alibaba/nacos/ribbon/NacosServerList.java
index f766945f..0d4fdbb8 100644
--- a/spring-cloud-alibaba-nacos-discovery/src/main/java/org/springframework/cloud/alibaba/nacos/ribbon/NacosServerList.java
+++ b/spring-cloud-alibaba-nacos-discovery/src/main/java/org/springframework/cloud/alibaba/nacos/ribbon/NacosServerList.java
@@ -44,8 +44,17 @@ public class NacosServerList extends AbstractServerList<NacosServer> {
 
 	@Override
 	public List<NacosServer> getInitialListOfServers() {
+		return getServers();
+	}
+
+	@Override
+	public List<NacosServer> getUpdatedListOfServers() {
+		return getServers();
+	}
+
+	private List<NacosServer> getServers() {
 		try {
-			List<Instance> instances = registration.getNacosNamingService().selectInstances(serviceId,true);
+			List<Instance> instances = registration.getNacosNamingService().selectInstances(serviceId, true);
 			return instancesToServerList(instances);
 		}
 		catch (Exception e) {
@@ -53,11 +62,6 @@ public class NacosServerList extends AbstractServerList<NacosServer> {
 		}
 	}
 
-	@Override
-	public List<NacosServer> getUpdatedListOfServers() {
-		return getInitialListOfServers();
-	}
-
 	private List<NacosServer> instancesToServerList(List<Instance> instances) {
 		List<NacosServer> result = new ArrayList<>(instances.size());
 		for (Instance instance : instances) {
['spring-cloud-alibaba-nacos-discovery/src/main/java/org/springframework/cloud/alibaba/nacos/ribbon/NacosServerList.java']