code: @Test public void testAsync(){
    CompletableFuture<Object> future=new CompletableFuture<>();
    AsyncContext asyncContext=new AsyncContextImpl(future);
    RpcContext rpcContext=RpcContext.getContext();
    Assert.assertFalse(rpcContext.isAsyncStarted());
    rpcContext.setAsyncContext(asyncContext);
    Assert.assertFalse(rpcContext.isAsyncStarted());
    RpcContext.startAsync();
    Assert.assertTrue(rpcContext.isAsyncStarted());
    asyncContext.write(new Object());
    Assert.assertTrue(future.isDone());
    rpcContext.stopAsync();
    Assert.assertTrue(rpcContext.isAsyncStarted());
  }
  