Setting Host header with net/http

main.go

package main

import (
	"fmt"
	"net/http"
	"io/ioutil"
)

func main() {
  client := &http.Client{}
  
  req, _ := http.NewRequest("GET", "http://httpbin.org/headers", nil)
  req.Host = "gophers"
  
  resp, _ := client.Do(req)
  
  defer resp.Body.Close()
  body, _ := ioutil.ReadAll(resp.Body)
  
  fmt.Printf("%s\n", body)
}

output.json

{
  "headers": {
    "Accept-Encoding": "gzip",
    "Host": "gophers",
    "User-Agent": "Go 1.1 package http"
  }
}