add Close() for relay handler

service/service.go

@@ -2,6 +2,7 @@ package service
 
 import (
 	"context"
+	"io"
 	"net"
 	"os/exec"
 	"strings"
@@ -105,6 +106,9 @@ func (s *defaultService) Close() error {
 	s.execCmds("pre-down", s.options.preDown)
 	defer s.execCmds("post-down", s.options.postDown)
 
+	if closer, ok := s.handler.(io.Closer); ok {
+		closer.Close()
+	}
 	return s.listener.Close()
 }