ReferenceError: next is not defined in controller product.js

[neemssoni]

you have not passed next as parameter, instead of this :
exports.product_create = function (req, res) { var content = new Product( { name: req.body.name, price: req.body.price } );

it should be :
exports.product_create = function (req, res, next) { var content = new Product( { name: req.body.name, price: req.body.price } );