skywalking springcloud gateway plugin not suppot springcloud greenwish sr4

[seifeHu]

Bug

• Which version of SkyWalking, OS and JRE?
  skywalking version 6.5
  springcloud version greenwish SR4 (Spring Cloud Gateway 2.1.4.RELEASE)
  springboot version2.1.10.release

I can not got trace form springcloud gateway in skywalking.
other springmvc app I can got trace In these versions

when I use spring springcloud version greenwish SR3(Spring Cloud Gateway 2.1.3.RELEASE
) 。Ｉ can got trace for Spring Cloud Gateway in Skywalking .

There are also some bugs in skywalking springcloud gateway plugin from springcloud sr3
I write customer filter for gateway. In filter do a spring feign method call in a mono
`
public GatewayFilter apply(Config config) {
return (exchange, chain) -> {

        Mono<Mono<Void>> objectMono = Mono.create(monoSink -> {
            executor.execute(new Runnable() {
                @Override
                public void run() {

                    CgiResult<JSONObject> cgiResult = null;
                    try {
                        cgiResult = iIotimTicketValidateService.validate(token, iotimTicket, din);
                    } catch (Exception e) {
                        logger.error("feign error:", e);
                    }

                    if (cgiResult != null && cgiResult.getErrCode() == 0) {

                        monoSink.success(chain.filter(exchange));
                    } else {
                        monoSink.success(unauthorizedResponse(exchange, cgiResult.getErrCode(), cgiResult == null ? "feign error" : cgiResult.getErrMsg()));
                    }
                }
            });
        });
        return objectMono;

}
This feign call not seen in one trace chain .

my call chain is
user ->gateway->feigncall_In_mono->feignRet->gatewayRouterToAppCall

[wu-sheng]

Gateway is a very complex scenario, @zhaoyuguang @ascrutae Please take a look.

@seifeHu Please try to debug first.