angular
  .module('myApp', [
    ...
  ])
  .run(
    [ '$rootScope', '$http',
      function ($rootScope,  $http) {

        $http.get('config/config.json').success(function(data) {
            $rootScope.config = data;
        });


      }
    ]
  )

angular.module('myApp')
    .controller('MainCtrl', function ($rootScope) {
      console.log($rootScope, $rootScope.config);
    })