Is there a way to dynamically generate sessionid for a request in api.ai

i have a nodejs rest api that hits api.ai wit a query. I want to generate a unique session ID for each user who accesses the app.

If I use the same session ID for all the requests I am afraid that the data(entities) of one request will be used for another request as the session ID is same.

So is there any way by which i can obtain an access troken from an agent in api.ai

via krish