@CheckReturnValue
    public HttpResponse cancel(String appName, String instanceId) {
        requireNonNull(appName, "appName");
        requireNonNull(instanceId, "instanceId");
        final String path = APPS + appName + '/' + instanceId;
        return webClient.delete(path);
    }
Deregisters the specified {@code instanceId} in {@code appName} from the Eureka registry.
eureka/src/main/java/com/linecorp/armeria/internal/common/eureka/EurekaWebClient.java