@CheckReturnValue
    public HttpResponse getInstance(String appName, String instanceId) {
        return sendGetRequest(APPS + requireNonNull(appName, "appName") + '/' +
                              requireNonNull(instanceId, "instanceId"));
    }
Retrieves the registry information whose application name is the specified {@code appName}
and instance ID is the specified {@code instanceId} from the Eureka.
eureka/src/main/java/com/linecorp/armeria/internal/common/eureka/EurekaWebClient.java