Q:

Connect Mongo add data to session

I am using connect mongo for login session. When a session is created it stores session data in mongo db session. But how can I store additional data in session like email id etc. 

A:

You have to check official documentation here.  You are able to add custom serialize of session.  Doc says:

Custom hook for serializing sessions to MongoDB.  This is helpful if
  you need to modify the session before writing it out. 

By default they have two ways to do it:

parse, stringify: they use JSON.parse() to unserialize to object and JSON.stringify() to serialize
default serializer: it goes through properties in session object and converts the cookie instance to an object, if possible and as well gets rid of the duplicate object under session.cookie.data property. 

You can create Your own serialize, You have to provide it in options parameter and You are done.