Golang "gopkg.in/ldap.v3" usage with on premises Active Directory

ldap.go

package main

import (
	"crypto/tls"
	"fmt"
	"log"

	"gopkg.in/ldap.v3"
)

func main() {
	username := "username@example.com"
	password := "password"
	ldapServer := "ldap.example.com"

	// Try to connect to LDAP server
	conn, err := ldap.Dial("tcp", fmt.Sprintf("%s:%d", ldapServer, 389))
	if err != nil {
		log.Fatal(err)
	}
	defer conn.Close()

	// Reconnect with TLS
	err = conn.StartTLS(&tls.Config{InsecureSkipVerify: true})
	if err != nil {
		log.Fatal(err)
	}

	// Bind as the user to verify their password
	// If this operation doesn't trigger an error then it's considered as a successful login
	err = conn.Bind(username, password)
	if err != nil {
		log.Fatal(err)
	}

	// Search for the given username
	// Query for other attributes related to the user
	searchRequest := ldap.NewSearchRequest(
		// The base domain name to search
		"dc=example,dc=com",
		ldap.ScopeWholeSubtree, ldap.NeverDerefAliases, 0, 0, false,
		// The filter to apply
		// See https://ldapwiki.com/wiki/LDAP%20Query%20Examples
		fmt.Sprintf("(&(objectClass=organizationalPerson)(userPrincipalName=%s))", username),
		// List of attributes to retrieve
		[]string{"cn", "c", "displayName", "userPrincipalName"},
		nil,
	)

	searchResult, err := conn.Search(searchRequest)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Println(searchResult)

	if len(searchResult.Entries) != 1 {
		log.Fatal("User does not exist or too many entries returned")
	}

	// Prints the result with 2 spaces for indentation
	searchResult.PrettyPrint(2)
}