Go语言中嵌套结构体如何正确赋值并转换为XML字符串？

package service

import (
    "encoding/xml"
    "fmt"
    "os"
    "testing"
)

type serverIP struct {
    IPv4 string `xml:"ipv4"`
    IPv6 string `xml:"ipv6"`
}

type server struct {
    ServerName string   `xml:"servername"`
    ServerIPs  []serverIP `xml:"serverip"`
}

type servers struct {
    XMLName  xml.Name `xml:"servers"`
    Version  string   `xml:"version,attr"`
    Servers  []server `xml:"server"`
}

func TestBuildNet(t *testing.T) {
    server1 := server{
        ServerName: "GLEKE",
        ServerIPs: []serverIP{
            {"127.0.0.1", "WWWWW"},
            {"127.0.0.2", "WWWWWSDFD"},
        },
    }

    serversData := servers{
        Version:  "1",
        Servers: []server{server1},
    }

    output, err := xml.MarshalIndent(serversData, "  ", "    ")
    if err != nil {
        fmt.Printf("error : %v\n", err)
        return
    }

    xmlString := string(output)
    fmt.Println(xml.Header + xmlString) // 输出XML字符串，包含XML声明
    os.Stdout.Write(output)             // 将XML输出到标准输出
}