# 12.6.1 获取域名的 NS记录

一个 DNS 请求常见的作用是找到域名的 **名称服务**，它们被存储在域名的 **NS 记录**中。这个功能将会在 `NSrecords.go` 的代码中介绍。

`NSrecords.go` 的代码将由俩部分展示。第一部分如下：

```go
package main

import(
    "fmt"
    "net"
    "os"
)

func main() {
    arguments := os.Args
    if len(arguments) == 1 {
        fmt.Println("Need a domain name!")
        return
    }
```

在这部分，您要检查是否至少有一个命令行参数，以便有可以运行的参数。

`NSrecords.go` 的剩余代码如下：

```go
    domain := arguments[1]
    NSs, err := net.LookupNS(domain)
    if err != nil {
        fmt.Println(err)
        return
    }

    for _, NS := range NSs {
        fmt.Println(NS.Host)
    }
}
```

`net.LookupNS()` 函数做了所有的工作，它将域名的 **NS 记录**作为 `net.NS` 类型的 slice 变量返回。这是打印 slice 的每个 `net.NS` 元素的 `Host` 字段的原因。

执行 `NSrecords.go` 将产生如下输出：

```
$ go run NSrecords.go mtsoukalos.eu
ns5.linode.com.
ns4.linode.com.
ns1.linode.com.
ns2.linode.com.
ns3.linode.com.
$ go run NSrecords.go www.mtsoukalos.eu
lookup www.mtsoukalos.eu on 8.8.8.8:53: no such host
```

您可以用 `host(1)` 工具验证上面输出的正确性：

```
$ host -t ns www.mtsoukalos.eu
www.mtsoukalos.eu has no NS record
$ host -t ns mtsoukalos.eu
mtsoukalos.eu name server ns3.linode.com.
mtsoukalos.eu name server ns1.linode.com.
mtsoukalos.eu name server ns4.linode.com.
mtsoukalos.eu name server ns2.linode.com.
mtsoukalos.eu name server ns5.linode.com.
```


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