go-elasticsearch w/ setting custom trusted CA certs and custom headers

main.go

package main

import (
	"encoding/base64"
	"crypto/x509"
	"fmt"
	"github.com/elastic/go-elasticsearch/v8"
	"io/ioutil"
	"log"
	"net/http"
	"os"
)

type CustomRoundTripper struct {
	http.RoundTripper
	Header http.Header
	transport *http.Transport
}

func (crt CustomRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
	for k, v := range crt.Header {
		log.Printf("Adding header: %s: %s", k, v)
		req.Header[k] = v
	}

	return crt.transport.RoundTrip(req)
}

func (crt *CustomRoundTripper) AddCACerts(path string) error {
	b, err := ioutil.ReadFile(path)
	if err != nil {
		log.Printf("Error reading additional ca certs in path %s / error %s", path, err)
		return err
	}

	ok := crt.transport.TLSClientConfig.RootCAs.AppendCertsFromPEM(b)
	if !ok {
		log.Printf("No certs were found in the additional ca cert path: %s", path)
		return err
	}

	return nil
}

func newCRT() (crt *CustomRoundTripper) {
	crt = new(CustomRoundTripper)
	crt.transport = http.DefaultTransport.(*http.Transport).Clone()
	crt.Header = make(http.Header)

	var err error
	crt.transport.TLSClientConfig.RootCAs, err = x509.SystemCertPool()
	if err != nil {
		panic(err)
	}
	return
}

func main() {
	esurl := os.Args[1]
	token := os.Args[2]
	cafile := os.Args[3]

	var err error

	crt := newCRT()
	//crt.Header.Set("Authorization", fmt.Sprintf("Bearer %s", token))
	crt.Header.Set("Authorization", fmt.Sprintf("ApiKey %s", base64.StdEncoding.EncodeToString([]byte(token))))
	log.Printf("%#v", crt.Header)


	crt.AddCACerts(cafile)

	log.Printf("transport: %#v", crt.transport)

	config := elasticsearch.Config{
		Addresses: []string{esurl},
		Transport: crt,
	}

	es, err := elasticsearch.NewClient(config)
	if err != nil {
		log.Printf("Error creating ES client: %s", err)
		os.Exit(1)
	}

	resp, err := es.Ping()
	if err != nil {
		fmt.Printf("Error pinging ES: %s\n", err)
		os.Exit(1)
	}

	fmt.Printf("Response: %s\n", resp)

}