chore: reverse the order of stopping services (#1159)

* chore: reverse the order of stopping services

* chore: reverse the order of stopping services

core/service/servicegroup.go

@@ -26,6 +26,7 @@ type (
 	}
 
 	// A ServiceGroup is a group of services.
+	// Attention: the starting order of the added services is not guaranteed.
 	ServiceGroup struct {
 		services []Service
 		stopOnce func()
@@ -41,7 +42,8 @@ func NewServiceGroup() *ServiceGroup {
 
 // Add adds service into sg.
 func (sg *ServiceGroup) Add(service Service) {
-	sg.services = append(sg.services, service)
+	// push front, stop with reverse order.
+	sg.services = append([]Service{service}, sg.services...)
 }
 
 // Start starts the ServiceGroup.