private CompletableFuture<AuthToken> login() {
        return tokenLoader.load().thenApply(loginResult -> loginResult.accessToken);
    }
A Nacos client that is responsible for
<a href="https://nacos.io/en-us/docs/auth.html">Nacos Authentication</a>.
nacos/src/main/java/com/linecorp/armeria/internal/nacos/LoginClient.java