private void checkCFCompletedSoon(CompletableFuture<?> cf) {
    try {
      unwrap(cf);
    } catch (RuntimeException e) {
      throw e;
    } catch (Throwable t) {
      throw new RuntimeException(t);
    }
  }
when you must parse a 2xx status to determine if the operation succeeded or not.
core/src/test/java/feign/AsyncFeignTest.java