我返回nil，为什么我的get request / google search收到错误消息

Question

是我的搜索引擎出了问题还是其他问题？尝试更改我的API密钥。还设置了断点以查看我的nil值是否来自“ let session = ..”中的错误。没有关于做什么的任何线索。

    googleSearch(term: "George Bush") { results in
        print(results)  }

}

func googleSearch（术语：字符串，回调：@转义（[[（标题：字符串，网址：字符串）]？）->无效）{     let urlString = String（格式：“ https://cse.google.com/cse?cx=016628067786358079133:2gm9usqzouc”，术语，Constants.searchEngineId，Constants.apiKey）     让encodeUrl = urlString.addingPercentEncoding（withAllowedCharacters：.urlQueryAllowed）

guard let url = URL(string: encodedUrl ?? urlString) else {
    print("invalid url \(urlString)")
    return
}

let request = NSMutableURLRequest(url: url, cachePolicy: .useProtocolCachePolicy, timeoutInterval: 10)
request.httpMethod = "GET"
request.setValue(Constants.bundleId, forHTTPHeaderField: "X-Ios-Bundle-Identifier")

let session = URLSession.shared
let datatask = session.dataTask(with: request as URLRequest) { (data, response, error) in
    guard
        error == nil,
        let data = data,
        let json = try? JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [String : Any]
        else {

            callback(nil)
            return
    }

    guard let items = json?["items"] as? [[String : Any]], items.count > 0 else {
        print("no results")
        return
    }

    callback(items.map { ($0["title"] as! String, $0["formattedUrl"] as! String) })
}


datatask.resume()
        }
}