How to set the ng-selected value in angularjs?

I am using the following code in my project. I have a select element in my angular js project. for options iam passing the json values using ng-repeat. but for ng-selected, I want to show the JSON first value.

I tried two options but it doesn't work for me. If anyone knows how to fix this please let me know.

My HTML code( option one and two):

  <select select2 id="environment" name="authorization" ng-model='addNlpStepForm.restfulEntity.authorization' class="md-form-control">
        <option ng-repeat="(key,value) in authorizationtype" value="{{key}}"
          ng-bind="value" ng-selected="addNlpStepForm.restfulEntity.authorization == 1"> 
        </option>
  </select>

<select select2 id="environment" name="authorization" ng-model='addNlpStepForm.restfulEntity.authorization' class="md-form-control">
        <option ng-repeat="(key,value) in authorizationtype" value="{{key}}"
          ng-bind="value" ng-selected="key == 1"> 
        </option>
  </select>

My JSON code:

AUTHORIZATION_TYPES = {
  1 : "None",
  2 : "Basic",
  3 : "Bearer",
};