//user login routes
    router.post('/authenticate', function(req,res){
        User.findOne({username:req.body.username}).select('email username password isPersonalTrainer _id isAdmin longitude latitude bodyFat height weight').exec(function(err,user){
            if(err) throw err;
                if(!user){
                    res.json({success:false, message:'No such user found!'});
                }else if (user) if (req.body.password) {
                    var validatePassword = user.comparePassword(req.body.password);
                    if (!validatePassword) {
                        res.json({success : false, message : 'Password incorrect'});
                    }else{
                        var token = jwt.sign({username: user.username, email: user.email, isPersonalTrainer: user.isPersonalTrainer, userId: user._id, isAdmin: user.isAdmin, longitude: user.longitude, latitude: user.latitude, bodyFat: user.bodyFat, height: user.height, weight: user.weight}, secret, {expiresIn: '24h'});
                        res.json({
                            success : true,
                            token:token,
                            userId:user._id,
                            longitude: user.longitude,
                            latitude: user.latitude
                            /// You have to res the token here. You can return the user id if you want but make sure to include the token
                        });
                    }
                }else{
                    res.json({success : false, message : 'No password provided!'});
                }
        })
    });