Using findByIdAndUpdate functionality inserts duplicate data in mongoDB?

Question

I am trying to update a data inside the MongoDB database . I am using findByIdAndUpdate function to do this , but a duplicate data gets inserted into the database . This is happening every time I am trying to update the data . Also used db.collection.update() but the same thing is happening . I have also used

findByIdAndUpdate(userId, { $set: {isPrime:true} },function(err,data)

It is also not working .

Code :

router.get('/getPremium',function(req,res){
  if(req.isAuthenticated()){
    var userId = req.user.id  ;
    console.log(req.user);
    console.log(req.user._id);
    User.findByIdAndUpdate(userId,{isPrime:true},function(err,data){
      if(err) throw err;
    })
    res.redirect('/');
  }else{
   res.redirect('/');
  }
})

I have also found answer to this findOneAndUpdate causing duplication problem but did not found it useful .

Any help regarding this will be helpful for me .