fix(gost): filter expected net.ErrClosed noise in service handler

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

go-gost/x/service/service.go

@@ -292,7 +292,9 @@ func (s *defaultService) Serve() error {
 			}
 
 			if err := s.handler.Handle(ctx, conn); err != nil {
+				if !errors.Is(err, net.ErrClosed) {
 					log.Error(err)
+				}
 				if v := xmetrics.GetCounter(xmetrics.MetricServiceHandlerErrorsCounter,
 					metrics.Labels{"service": s.name, "client": clientIP}); v != nil {
 					v.Inc()