如何在使用Feign builder时让Spring sleuth工作

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-sleuth</artifactId>
</dependency>

@FeignClient(name = "example-service", configuration = FeignConfig.class)
public interface ExampleFeignClient {
    // Feign方法定义
}

@Configuration
public class FeignConfig implements RequestInterceptor {
    
    @Override
    public void apply(RequestTemplate template) {
        Span currentSpan = tracer.currentSpan();
        if (currentSpan != null) {
            template.header("X-B3-TraceId", currentSpan.context().traceIdString());
            template.header("X-B3-SpanId", currentSpan.context().spanIdString());
        }
    }
}

spring:
  sleuth:
    sampler:
      probability: 1.0