Update pingpong.py

pingpong.py

@@ -15,7 +15,7 @@ def sendPingTask():
 
 def sendPing():
     print("sendPing")
-    url = os.getenv("WEBHOOK_URL")
+    url = os.environ.get("WEBHOOK_URL")
     headers = {
         "Content-Type": "application/json"
     }