To receive conversation exit events:
In the left navigation, click the + icon by the Intents menu item.
Give the intent a name (like Exit Conversation) and click on the Events section.
Enter actions_intent_CANCEL in the Add event field.
Either specify a response under Response or set up your own response for this intent in your webhook code.
Enable Set this intent as end of conversation.
Click Save.
In the left navigation, click Integrations.
Choose Google Assistant and click Update draft, then Test to make sure the changes are reflected in your project.
More documentation and information can be found in [1].
[1]:https://developers.google.com/assistant/conversational/conversation-exits#dialogflow