Spring Boot - handle rest call parallelly

Question

How can I handle rest calls parallely in spring boot ?
I created new spring boot 2.x application with one dependency

spring-boot-starter-web

Then I created basic controller like this

@RestController
@RequestMapping("/api/test")
public class HomeController {

    private static final Logger logger = LoggerFactory.getLogger(HomeController.class);

    @GetMapping
    public void longRunningMethod() throws InterruptedException {
        logger.info("long running method start");
        Thread.sleep(6000);
        logger.info("long running method finished");
    }
}

I run application (on localhost), open two web browsers and call it simultaneously.
I was expecting those calls will run in two separate threads paralelly hence finish roughly about the same time but here's console output.

2018-12-09 12:48:08.633  INFO 12192 --- [io-8080-exec-10] c.c.m.controller.HomeController          : long running method start
2018-12-09 12:48:14.634  INFO 12192 --- [io-8080-exec-10] c.c.m.controller.HomeController          : long running method finished
2018-12-09 12:48:14.683  INFO 12192 --- [io-8080-exec-10] c.c.m.controller.HomeController          : long running method start
2018-12-09 12:48:20.683  INFO 12192 --- [io-8080-exec-10] c.c.m.controller.HomeController          : long running method finished

As you can see calls were sequentially second call waits until first finish. What am I missing ?
Thanks