var token = jwt.sign({email_id:'123@gmail.com'}, "Stack", {
expiresIn: "10h" // it will be expired after 10 hours
//expiresIn: "20d" // it will be expired after 20 days
//expiresIn: 120 // it will be expired after 120ms
//expiresIn: "120s" // it will be expired after 120s
});