How to push context from angular to dialogflow

I am building a chatbot, in which frontend is angular and bot is dialogflow, so basically I have to mail the whole conversation to user through mail. I am able to collect all the conversation in a list in angular through the data I am getting from dialogflow, but I want to pass that list in dialogflow as parameter in custom data so that API can get the whole conversation and mail it to user.
I am unable to push the list data to dialogflow.
Please help

Source: AngularJS Questions