private void start(final List<String> servers) {
        this.login(servers);
        this.executorService.scheduleWithFixedDelay(() -> this.login(servers), 5000, 5000, TimeUnit.MILLISECONDS);
    }
server login.

@param servers server list.
shenyu-sync-data-center/shenyu-sync-data-http/src/main/java/org/apache/shenyu/sync/data/http/AccessTokenManager.java