check if the task is future or ongoing to send email and notification on assign user

app/Http/Controllers/TasksController.php

@@ -91,7 +91,7 @@ class TasksController extends Controller
 
             $user = User::find($id);
 
-            if($user) {
+            if($user && Carbon::now()->lessThanOrEqualTo($task->end)) {
                 $task->users()->attach($id);
 
                 broadcast(new VolunteerAssignedToTask(