问swift 5上POST请求的一些问题

EN

init()
{
    getSongs()
}

func getSongs()
{
    let url = URL(string: "http://31.31.196.187:5000/search")
    
    guard let requestUrl = url else { fatalError() }
    var request = URLRequest(url: requestUrl)
    request.httpMethod = "POST"
    let postString:[String:Any] = [
        "song_url": "https://music.yandex.ru/album/4066489/track/33274678",
        "service": "Spotify"
       ]
    let jsonData = try? JSONSerialization.data(withJSONObject: postString, options: JSONSerialization.WritingOptions())
    
    request.httpBody = jsonData

    
    URLSession.shared.dataTask(with: request) { (data, response, error) in

        guard error == nil else
        {
            print ("Error!!!")
            return
            
        }
        if let data = data, let dataString = String(data: data, encoding: .utf8) {
                    print("Response data string:\n \(dataString)")
            self.get = dataString
                }
    } .resume()
}