AWS es Proxy in go

main.go

package main

import (
	"bytes"
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"net"
	"net/http"
	"net/http/httputil"
	"strings"
	"time"

	"github.com/aws/aws-sdk-go/aws/credentials"
	"github.com/aws/aws-sdk-go/aws/signer/v4"
	"github.com/aws/aws-sdk-go/private/protocol/rest"
)

func main() {
	flag.Parse()
	if len(flag.Args()) != 1 {
		log.Fatalln("Please provide an AWS es cluster URL.")
	}

	var esCluster = flag.Args()[0]
	if esCluster == "" {
		log.Fatalln("Please provide an AWS es cluster URL.")
	}

	if hosts, err := net.LookupHost(esCluster); err != nil {
		log.Printf("Failed to resolve es cluster: %v.\n", err)
	} else {
		log.Printf("%q resolves to %#v.\n", esCluster, hosts)
	}

	var creds *credentials.Credentials
	var region = strings.Split(esCluster, ".")[1]

	fmt.Printf(`
__________       _________    _________________    ________                            ______
___    |_ |     / /_  ___/    ___  ____/_  ___/    ___  __ \________________  ______  ____  /
__  /| |_ | /| / /_____ \     __  __/  _____ \     __  /_/ /_  ___/  __ \_  |/_/_  / / /_  /
_  ___ |_ |/ |/ / ____/ /     _  /___  ____/ /     _  ____/_  /   / /_/ /_>  < _  /_/ / /_/
/_/  |_|___/|__/  /____/      /_____/  /____/      /_/     /_/    \____//_/|_| _\__, / (_)
                                                                               /____/
Connected to %s
AWS ES cluster available at http://127.0.0.1:9200
Kibana available at http://127.0.0.1:9200/_plugin/kibana/
`, esCluster)

	creds = credentials.NewSharedCredentials("", "")
	if _, err := creds.Get(); err != nil {
		creds = credentials.NewEnvCredentials()
		if _, err = creds.Get(); err != nil {
			log.Fatalf("Failed to load credentials: %v", err)
		}
	}
	signer := v4.NewSigner(creds)

	director := func(req *http.Request) {
		req.URL.Scheme = "https"
		req.Host = esCluster
		req.URL.Host = esCluster
		req.Header.Set("Connection", "close")
		if req.Header.Get("Expect") != "" {
			req.Header.Del("Expect")
		}

		if strings.Contains(req.URL.RawPath, "%2C") {
			req.URL.RawPath = rest.EscapePath(req.URL.RawPath, true)
		}

		fmt.Printf("%s %s\n", req.Method, req.URL.Path)
		t := time.Now()
		req.Header.Set("Date", t.Format(time.RFC3339))

		if req.Method != http.MethodGet && req.Method != http.MethodHead {
			buf, err := ioutil.ReadAll(req.Body)
			if err != nil {
				log.Fatal(err)
			}
			req.Body = ioutil.NopCloser(bytes.NewReader(buf))

			if _, err := signer.Sign(req, bytes.NewReader(buf), "es", region, t); err != nil {
				log.Printf("failed to sign: %v", err)
			}
		} else {
			buf := bytes.Buffer{}
			req.Body = ioutil.NopCloser(&buf)
			if _, err := signer.Sign(req, bytes.NewReader(buf.Bytes()), "es", region, t); err != nil {
				log.Printf("failed to sign: %v", err)
			}
		}

	}
	proxy := &httputil.ReverseProxy{Director: director}
	log.Printf("[INFO] %v", http.ListenAndServe(":9200", proxy))
}

Thanks, it worked instantly !
For those who start from scratch like me:

# install go
curl -O https://dl.google.com/go/go1.15.3.linux-amd64.tar.gz
sudo tar -C /usr/local -xzf go1.15.3.linux-amd64.tar.gz
export PATH=$PATH:/usr/local/go/bin
# download script
mkdir es_proxy
cd es_proxy
curl -O https://gist.githubusercontent.com/nicolai86/5ffe8905ab2c16cf0b3eb8f054bae456/raw/30e6a92ed1f09e052ec0ba695ce34f8281dc4f2d/main.go
go get -d .
go run main.go search-XXX.es.amazonaws.com