How do you make a request to google-api using node.js and Express? Getting Request is not defined Error

I am working on a node.js server and want to call the Google Shopping Service and retrieve results for a search query. I think I am applying the search query string correctly, but I am getting a 500 Reference Error: Request is not defined. My code is below:

googleShoppingService.js

//Shopping Search Factory

module.exports = function(productSearch){
    return new productKey('---API-KEY-GOES-HERE---');
};
//constructor

function productKey(key) {

    this.key=key;
}
// Search API

function toJSON(str){
    var result;
    try {
        result=JSON.parse(str);
    } catch(err){}
    return result;
 }

productKey.prototype.search = function (req, done) {
    request.get('https://www.googleapis.com/shopping/search/v1/public/products')
        .send({key:this.key})
        .send({country:'US'})
        .send({q:req.body.searchQuery.value})
        .end(function (err, res) {
            var body = toJSON(res.text);
            var result = body && body.product || [];
            return done(err, result);
        });
};

app.js

var productSearch = require('./apis/googleShoppingSearch.js');
var products = productSearch('---API-KEY-GOES-HERE---')

app.get('/productResults', function(req, res){
    products.search(process.argv[2], function (err, results) {
        var returnedData = ""
        for (var i=0;i < results.length; i++) {
            returnedData += (results[i].title + '<br />')
        }
        res.send (returnedData)
    });
});

Any suggestions to solve my problem would be greatly appreciated. Thanks for the help in advance.