Check if SNI is blocked with Golang

sni-block-check.go

package main

import (
	"crypto/tls"
	"log"
	"net"
)

const hostname = "www.google.com"
const request = "GET / HTTP/1.1\r\nHost: " + hostname + "\r\nConnection: close\r\n\r\n"

func main() {
	dialConn, err := net.Dial("tcp", "172.217.13.132:443") // google ip
	if err != nil {
		log.Fatalf("cannot dial: %s", err)
	}
	config := tls.Config{ServerName: hostname}
	tlsConn := tls.Client(dialConn, &config)
	_, err = tlsConn.Write([]byte(request))
	if err != nil {
		log.Fatalf("cannot write: %s", err)
	}
	buffer := make([]byte, 1024)
	_, err = tlsConn.Read(buffer)
	if err != nil {
		log.Fatalf("cannot read: %s", err)
	}
	log.Println(string(buffer))
}