Node.JS How to Add Require() inside CreateContext or RunInContext

I am trying to figure out how to add access to certain node modules from inside CreateContext() or RunInContext().

Every time I try, I get an undefined variable error

var s = new Sandbox();
            var obj4 = 'hello = "world"; util.log("Hello " + hello);'

            //Execute Javascript and Respond
            s.run(obj4, function (output) {
                logic = output.result;
                res.send(logic);
            });