title: iOS Swift verify receipt JSON fetch issue
body: <p>While testing my in-app subscription, I find out that the <code>latest_receipt</code> is possible to get. When it comes to running the app at the release mode on App Store, all new app users find the exception at the line of code : </p>
  
  <pre><code>  let latestReceipt = responseTransaction.object(forKey: "latest_receipt") as! String
  </code></pre>
  
  <p>Would you please tell me under IAP documentation, what is the possible state of this the field <code>latest_receipt</code>? and it turns empty or null responses? </p>
  
  <p>When I use sandbox, it often gives : </p>
  
  <pre><code>{
      "latest_receipt": "MIIbngYJKoZIhvcNAQcCoIIbj...",
      "status": 0,
      "receipt": {
          "download_id": 0,
          "receipt_creation_date_ms": "1486371475000",
          "application_version": "2",
          "app_item_id": 0,
          "receipt_creation_date": "2017-02-06 08:57:55 Etc/GMT",
          "original_purchase_date": "2013-08-01 07:00:00 Etc/GMT",
          "request_date_pst": "2017-02-06 04:41:09 America/Los_Angeles",
          "original_application_version": "1.0",
          "original_purchase_date_pst": "2013-08-01 00:00:00 America/Los_Angeles",
          "request_date_ms": "1486384869996",
          "bundle_id": "com.yourcompany.yourapp",
          "request_date": "2017-02-06 12:41:09 Etc/GMT",
          "original_purchase_date_ms": "1375340400000",
          "in_app": [{
              "purchase_date_ms": "1486371474000",
              "web_order_line_item_id": "1000000034281189",
              "original_purchase_date_ms": "1486371475000",
              "original_purchase_date": "2017-02-06 08:57:55 Etc/GMT",
              "expires_date_pst": "2017-02-06 01:00:54 America/Los_Angeles",
              "original_purchase_date_pst": "2017-02-06 00:57:55 America/Los_Angeles",
              "purchase_date_pst": "2017-02-06 00:57:54 America/Los_Angeles",
              "expires_date_ms": "1486371654000",
              "expires_date": "2017-02-06 09:00:54 Etc/GMT",
              "original_transaction_id": "1000000271014363",
              "purchase_date": "2017-02-06 08:57:54 Etc/GMT",
              "quantity": "1",
              "is_trial_period": "false",
              "product_id": "com.yourcompany.yourapp",
              "transaction_id": "1000000271014363"
          }],
          "version_external_identifier": 0,
          "receipt_creation_date_pst": "2017-02-06 00:57:55 America/Los_Angeles",
          "adam_id": 0,
          "receipt_type": "ProductionSandbox"
      },
  </code></pre>
  
  <p>When pushing into production, it gives something like : </p>
  
  <pre><code> {'environment': 'Production',
    'receipt': {'adam_id': 1465637208,
                'app_item_id': 1465637208,
                'application_version': '33',
                'bundle_id': 'gogoyuedu.testing.anc',
                'download_id': 7505071111117518,
                'in_app': [],
                'original_application_version': '31',
                'original_purchase_date': '2019-09-30 05:16:04 Etc/GMT',
                'original_purchase_date_ms': '1569820564000',
                'original_purchase_date_pst': '2019-09-29 22:16:04 '
                                              'America/Los_Angeles',
                'receipt_creation_date': '2019-10-02 08:49:40 Etc/GMT',
                'receipt_creation_date_ms': '1570006180000',
                'receipt_creation_date_pst': '2019-10-02 01:49:40 '
                                             'America/Los_Angeles',
                'receipt_type': 'Production',
                'request_date': '2019-10-02 08:49:47 Etc/GMT',
                'request_date_ms': '1570006187285',
                'request_date_pst': '2019-10-02 01:49:47 America/Los_Angeles',
               'version_external_identifier': 832979108},
    'status': 0}
  </code></pre>
  
  <p>At my swift method, should I get purchases record under attribute <code>in_app</code> instead of <code>latest_receipt_info</code> ? </p>
  
  <p>If so, how can I get my latest receipt at the field <code>in_app</code>  ? </p>