I was a newbie, started developing a sample chatbot using angular and DialogFlow, I was not able to access the client access token. And I have tried other ways like gcloud auth print access token, and have gone through Google service account. Any answer is welcome, Thanks in advance.
Dialogflow v2 no longer uses developer/client access tokens. Those were for v1 only.
You need to setup authentication and download private keys now to access the API endpoints.
If you are using a library, you should just be able to make the downloaded keys available to your library. If you are doing it yourself, you will need to generate an OAuth 2 auth token using these keys.