var parentColl *bongo.Collection
var childColl *bongo.Collection
type parent struct{
	bongo.DocumentBase `bson:",inline"`
	Childs []*Child
}
type Child struct{
	bongo.DocumentBase `bson:",inline"`
	ParentID bson.ObjectId
	Status int
	diffTracker *bongo.DiffTracker
}

func Test_Bongo(t *testing.T){
	parentColl=utils.Bconn.Collection("parent")
	childColl=utils.Bconn.Collection("child")
	parent:=new(parent)
	parentColl.Save(parent)
	child:=new(Child)
	child.ParentID=parent.Id
	childColl.Save(child)

	for i:=1;i<100;i++{
		child.Status=i
		childColl.Save(child) //will invoke CascadeSave  using (goroutine CascadeSave)
	//code: https://github.com/go-bongo/bongo/blob/master/collection.go#L147
	}

	//**the end**: len(parent.Childs)!=1 or parent.Childs[0].Status!=99
}
func (c *Child) GetCascade(collection *bongo.Collection) []*bongo.CascadeConfig {
	connection := collection.Connection
	rel :=c
	cascadeMulti := &bongo.CascadeConfig{
		Collection:  connection.Collection("parent"),
		//Properties:  []string{"name","orgname","status"},
		Data:rel,
		ThroughProp: "childs",
		RelType:     bongo.REL_MANY,
		Query: bson.M{
			"_id": c.ParentID,
		},
	}
	if c.diffTracker!=nil && c.diffTracker.Modified("ParentID") {
		origId, _ := c.diffTracker.GetOriginalValue("ParentID")
		if origId != nil {
			oldQuery := bson.M{
				"_id": origId,
			}
			cascadeMulti.OldQuery = oldQuery
		}

	}
	return []*bongo.CascadeConfig{ cascadeMulti}
}

	for i:=1;i<20;i++{
		cloneChild:=*child
		cloneChild.Status=i
		childColl.Save(&cloneChild) 
	}
	time.Sleep(2*time.Second)