Failed to resolve service with Spring Cloud LoadBalancer

Question

I followed this guide to implement a simple client-side load balancer in a Spring Boot application. Below is the code:

@RestController
class MyController(
    val loadBalancedWebClientBuilder: WebClient.Builder
) { 
    private fun makeRequest() {
        loadBalancedWebClientBuilder.build().post()
                .uri(URI("http://my-service/endpoint"))
                .body(BodyInserters.fromValue("{ \"data\" = \"data\" }"))
                .retrieve()
                .bodyToMono(String::class.java)
                .block()
    }
}

Here is the WebClient configuration:

@Configuration
@LoadBalancerClient(name = "my-service", configuration = [LoadBalancerConfig::class])
class WebClientConfig {
    @LoadBalanced
    @Bean
    fun webClientBuilder(): WebClient.Builder {
        return WebClient.builder()
    }
}

And the load balancer configuration:

class LoadBalancerConfig {
    @Bean
    @Primary
    fun serviceInstanceListSupplier(): ServiceInstanceListSupplier {
        return ServiceInstanceListSupplerImpl("my-service")
    }
}

class ServiceInstanceListSupplerImpl(private val serviceId: String) : ServiceInstanceListSupplier {
    override fun getServiceId(): String {
        return serviceId
    }

    override fun get(): Flux<List<ServiceInstance>> {
        return Flux.just(listOf("http://localhost").mapIndexed { index, s ->
            DefaultServiceInstance(index.toString(), serviceId, s, 8088, true) })
    }

}

Finally, in the configuration file I have the below:

spring:
  cloud:
    discovery:
      client:
        simple:
          instances:
            my-service[0].uri: http://localhost:8088

When running the above, the following exception gets thrown:

org.springframework.web.reactive.function.client.WebClientRequestException: Failed to resolve 'my-service' after 4 queries ; nested exception is java.net.UnknownHostException: Failed to resolve 'my-service' after 4 queries 
    at org.springframework.web.reactive.function.client.ExchangeFunctions$DefaultExchangeFunction.lambda$wrapException$9(ExchangeFunctions.java:141) ~[spring-webflux-5.3.24.jar:5.3.24]
    Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Error has been observed at the following site(s):
    *__checkpoint ⇢ Request to POST http://my-service/endpoint [DefaultWebClient]
Original Stack Trace:
        at org.springframework.web.reactive.function.client.ExchangeFunctions$DefaultExchangeFunction.lambda$wrapException$9(ExchangeFunctions.java:141) ~[spring-webflux-5.3.24.jar:5.3.24]
        at reactor.core.publisher.MonoErrorSupplied.subscribe(MonoErrorSupplied.java:55) ~[reactor-core-3.4.25.jar:3.4.25]
        at reactor.core.publisher.Mono.subscribe(Mono.java:4490) ~[reactor-core-3.4.25.jar:3.4.25]
        at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onError(FluxOnErrorResume.java:103) ~[reactor-core-3.4.25.jar:3.4.25]
        at reactor.core.publisher.FluxPeek$PeekSubscriber.onError(FluxPeek.java:222) ~[reactor-core-3.4.25.jar:3.4.25]
        at reactor.core.publisher.FluxPeek$PeekSubscriber.onError(FluxPeek.java:222) ~[reactor-core-3.4.25.jar:3.4.25]
        at reactor.core.publisher.FluxPeek$PeekSubscriber.onError(FluxPeek.java:222) ~[reactor-core-3.4.25.jar:3.4.25]
        at reactor.core.publisher.MonoNext$NextSubscriber.onError(MonoNext.java:93) ~[reactor-core-3.4.25.jar:3.4.25]
        at reactor.core.publisher.MonoFlatMapMany$FlatMapManyMain.onError(MonoFlatMapMany.java:204) ~[reactor-core-3.4.25.jar:3.4.25]
        at reactor.core.publisher.SerializedSubscriber.onError(SerializedSubscriber.java:124) ~[reactor-core-3.4.25.jar:3.4.25]
        ...
        

Any clue what might be wrong?