Error Message with Angular

angular.module("todoListApp",[]) //name of app and definitions of dependeices. Empty tells angular to create file. If 2nd arg left off. will look for totdolist app instead of creating it. 

.controller('mainCtrl',function ($scope,dataService){
    $scope.helloService = dataService.helloLog();
    $scope.helloWorld = function (){
        console.log("Hello World, this is the main cotnroller speaking!");
      }
    $scope.whatsgoodWorld = function ($scope) {
        console.log("Whats good world?!");
    }

  $scope.learningngchange = function (){
    console.log("An Input Changed");
  }

   dataService.getTodos(function (response){
    console.log (response.data);
      $scope.todos = response.data;
  });

})//Name and call back function

.service("dataService", function($http){
    this.helloLog = function(){
        console.log("Hello, this is my first service!");
      };// this attaches method to service

  this.getTodos = function (callback){$http.get('mock/todos.json')
  .then(callback)
     } //1st arg to get is url to filepath. 'then' executes after response from server
});