从Swift中的Firebase Realtime DB获取当前服务器时间

我使用此函数从firebase服务器获取Servertime偏移量:

getCurrentServerTime(){ (date) in

        let serverDate = Date(timeIntervalSince1970: date)
        print(serverDate)
}

public func getCurrentServerTime(completionHandler:@escaping (Double) -> ()){
        Database.database().reference(withPath: ".info/serverTimeOffset").observeSingleEvent(of: .value) { (snapshot) in
            if let time = snapshot.value as? Double{
                completionHandler(Date().timeIntervalSince1970 + time)
            }else{
                completionHandler(0)

            }
        }
    }