Golang Xml Unmarshal，没有 Value

type VastHtml struct {
     VAST struct {
             Version string `xml:"version,attr"`
             Ad      struct {
                     Id     string `xml:"id,attr"`
                     InLine struct {
                             AdSystem    string   `xml:"AdSystem"`
                             AdTitle     string   `xml:"AdTitle"`
                             Description string   `xml:"Description"`
                             Error       string   `xml:"Error"`
                             Impression  []string `xml:"Impression"`
                             Creatives   struct {
                                     Creative []struct {
                                             Sequence string `xml:"sequence,attr"`
                                             Id       string `xml:"id,attr"`
                                             Linear   struct {
                                                     Duration       string `xml:"Duration"`
                                                     TrackingEvents struct {
                                                             Tracking []string `xml:"Tracking"`
                                                     } `xml:"TrackingEvents"`
                                                     VideoClicks struct {
                                                             ClickThrough string   `xml:"ClickThrough"`
                                                             CustomClick  []string `xml:"CustomClick"`
                                                     } `xml:"VideoClicks"`
                                                     MediaFiles struct {
                                                             MediaFile []struct {
                                                                     Delivery string `xml:"delivery,attr"`
                                                                     Bitrate  string `xml:"bitrate,attr"`
                                                                     Width    string `xml:"width,attr"`
                                                                     Height   string `xml:"height,attr"`
                                                                     Type     string `xml:"type,attr"`
                                                             } `xml:"MediaFile"`
                                                     } `xml:"MediaFiles"`
                                             } `xml:"Linear"`
                                             CompanionAds struct {
                                                     Companion []struct {
                                                             Width                 string `xml:"width,attr"`
                                                             Height                string `xml:"height,attr"`
                                                             StaticResource        string `xml:"StaticResource"`
                                                             TrackingEvents        string `xml:"TrackingEvents"`
                                                             CompanionClickThrough string `xml:"CompanionClickThrough"`
                                                     } `xml:"Companion"`
                                             } `xml:"CompanionAds"`
                                     } `xml:"Creative"`
                             } `xml:"Creatives"`
                             Extensions string `xml:"Extensions"`
                     } `xml:"InLine"`
             } `xml:"Ad"`
     } `xml:"VAST"`

}

func main() 
{

    resp, err := http.Get("http://ad3.liverail.com/?LR_PUBLISHER_ID=1331&LR_CAMPAIGN_ID=229&LR_SCHEMA=vast2")

    if err != nil {
        fmt.Println(err)
        os.Exit(1)
    }

    defer resp.Body.Close()

   xmlDataFromHttp, err := ioutil.ReadAll(resp.Body) 

    if err != nil {
        fmt.Println(err)
        os.Exit(1)
    }
   fmt.Println(os.Stdout, string(xmlDataFromHttp))

// read xml http response

   var xmlData VastHtml
   err = xml.Unmarshal(xmlDataFromHttp, &xmlData)
     if err != nil {
           panic(err)
         }

fmt.Printf("XML===>: ", xmlData.VAST)

 }

在Unmarshaling我从一个只给出结构但没有任何值的URL得到的XmlVast之后，你好 . 即使我在文件中复制XmlVast的内容，我尝试解组它，它给我相同的响应结构没有任何 Value .

先感谢您 .