Как проверить состояние google play in-app покупки на сервере?

https://www.googleapis.com/androidpublisher/v2/applications/<packageName>/purchases/products/<productId>/tokens/<token>?key=<apiKey>

{
    "error":  {
    "errors":  [
            {
                "domain": "global",
                "reason": "required",
                "message": "Login Required",
                "locationType": "header",
                "location": "Authorization"
            }
        ],
        "code": 401,
        "message": "Login Required"
    }
}