var token = jwt.sign({email_id:'123@gmail.com'}, "Stack", {
expiresIn: '24h' // expires in 24 hours
});
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
});