How Can I Perform DNS Lookups in Go with a Custom DNS Server?

Lookup Functions in Go

Many network-related operations rely on DNS lookups to resolve hostnames to IP addresses and other information. Golang provides a set of convenient functions in the net package for performing DNS lookups, including LookupAddr and LookupTXT, which return the corresponding IP addresses or text records for a given hostname.

One limitation of these functions is that they typically rely on the system's resolvers configured in /etc/resolv.conf. While this is sufficient in most cases, there may be instances where you need to specify a specific DNS server to perform the lookup.

Lookup Functions with Custom DNS Server

Unfortunately, the standard Go library does not currently offer functions like LookupAddrWithServer or LookupTXTWithServer that allow you to specify a custom DNS server. However, there are several third-party libraries that provide this functionality, including the popular github.com/miekg/dns.

The following modified example from the answer given by @holys demonstrates how you can use the miekg/dns library to perform DNS lookups with a specified server:

package main

import (
    "fmt"
    "log"

    "github.com/miekg/dns"
)

func main() {
    target := "example.com"
    server := "8.8.8.8"

    c := dns.Client{}
    m := dns.Msg{}
    m.SetQuestion(target, dns.TypeA)
    r, t, err := c.Exchange(&m, server+":53")
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("Took %v", t)
    if len(r.Answer) == 0 {
        log.Fatal("No results")
    }
    for _, ans := range r.Answer {
        arecord := ans.(*dns.A)
        fmt.Printf("%s", arecord.A)
    }
}

This example uses the github.com/miekg/dns library to perform an A record lookup for example.com using the specified DNS server at 8.8.8.8. By leveraging third-party libraries like miekg/dns, you can extend the functionality provided by the Go standard library to meet your specific requirements.

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