refractor files and improve aria2 process killing, needs improvement

core/utils/general/shutdown.py

@@ -0,0 +1,16 @@
+from core.utils.data.state import state
+import threading
+
+
+shutdown_event = threading.Event()
+
+def kill_aria2server():
+    if state.aria2process:
+        state.aria2process.kill()
+        if state.debug:
+            print("\nKilled Aria2")
+
+
+def closehelper():
+    shutdown_event.set()
+    kill_aria2server()