diff --git a/dag/v2/dag.go b/dag/v2/dag.go
index 3d41db8..f3e2181 100644
--- a/dag/v2/dag.go
+++ b/dag/v2/dag.go
@@ -52,6 +52,7 @@ type DAG struct {
 	taskManager storage.IMap[string, *TaskManager]
 	finalResult func(taskID string, result Result)
 	mu          sync.Mutex
+	Error       error
 }
 
 func NewDAG(finalResultCallback func(taskID string, result Result)) *DAG {
@@ -62,14 +63,22 @@ func NewDAG(finalResultCallback func(taskID string, result Result)) *DAG {
 	}
 }
 
-func (tm *DAG) AddNode(nodeID string, handler func(payload json.RawMessage) Result) {
+func (tm *DAG) AddNode(nodeID string, handler func(payload json.RawMessage) Result) *DAG {
+	if tm.Error != nil {
+		return tm
+	}
 	tm.nodes.Set(nodeID, &Node{ID: nodeID, Handler: handler})
+	return tm
 }
 
-func (tm *DAG) AddEdge(from string, targets ...string) error {
+func (tm *DAG) AddEdge(from string, targets ...string) *DAG {
+	if tm.Error != nil {
+		return tm
+	}
 	node, ok := tm.nodes.Get(from)
 	if !ok {
-		return fmt.Errorf("node not found %s", from)
+		tm.Error = fmt.Errorf("node not found %s", from)
+		return tm
 	}
 	for _, target := range targets {
 		if targetNode, ok := tm.nodes.Get(target); ok {
@@ -77,7 +86,7 @@ func (tm *DAG) AddEdge(from string, targets ...string) error {
 			node.Edges = append(node.Edges, edge)
 		}
 	}
-	return nil
+	return tm
 }
 
 func (tm *DAG) GetNextNodes(key string) ([]*Node, error) {
@@ -116,7 +125,6 @@ func (tm *DAG) formHandler(w http.ResponseWriter, r *http.Request) {
 		taskID := mq.NewID()
 		manager := NewTaskManager(tm)
 		tm.taskManager.Set(taskID, manager)
-		go manager.Run()
 		payload := fmt.Sprintf(`{"email": "%s", "age": "%s", "gender": "%s"}`, email, age, gender)
 		manager.Trigger(taskID, "NodeA", json.RawMessage(payload))
 		http.Redirect(w, r, "/result?taskID="+taskID, http.StatusFound)
@@ -143,9 +151,6 @@ func (tm *DAG) taskStatusHandler(w http.ResponseWriter, r *http.Request) {
 }
 
 func (tm *DAG) Start(addr string) {
-	tm.AddEdge("NodeA", "NodeB")
-	tm.AddEdge("NodeB", "NodeC")
-	tm.AddEdge("NodeC", "Result")
 	http.HandleFunc("/form", tm.formHandler)
 	http.HandleFunc("/result", tm.resultHandler)
 	http.HandleFunc("/task-result", tm.taskStatusHandler)
diff --git a/dag/v2/task_manager.go b/dag/v2/task_manager.go
index 45f13ad..2cab763 100644
--- a/dag/v2/task_manager.go
+++ b/dag/v2/task_manager.go
@@ -16,7 +16,6 @@ type TaskState struct {
 	Timestamp     time.Time
 	Result        Result
 	targetResults storage.IMap[string, Result]
-	my            sync.Mutex
 }
 
 type nodeResult struct {
@@ -46,6 +45,7 @@ func NewTaskManager(dag *DAG) *TaskManager {
 		resultQueue: make(chan nodeResult, 100),
 		dag:         dag,
 	}
+	go tm.Run()
 	go tm.WaitForResult()
 	return tm
 }
diff --git a/examples/v2.go b/examples/v2.go
index fbe02cd..dc52e4d 100644
--- a/examples/v2.go
+++ b/examples/v2.go
@@ -54,5 +54,11 @@ func main() {
 	dag.AddNode("NodeB", NodeB)
 	dag.AddNode("NodeC", NodeC)
 	dag.AddNode("Result", Result)
+	dag.AddEdge("NodeA", "NodeB")
+	dag.AddEdge("NodeB", "NodeC")
+	dag.AddEdge("NodeC", "Result")
+	if dag.Error != nil {
+		panic(dag.Error)
+	}
 	dag.Start(":8080")
 }