对于nslookup命令,它有nslookup somewhere.com some.dns.server.
但是,似乎golang dnsclient只加载配置 /etc/resolv.conf
代码在这里:https://golang.org/src/net/dnsclient_unix.go#L225
golang标准库是否提供类似的功能
func LookupTXT(name string, dnsServer string) (txt []string, err error)？
requirement:1.不要更改默认值/etc/resolv.conf.