how to count http request with goroutine and channel - in 20 code lines [golang] [20lines]

main.go

package main

import "fmt"
import "net/http"

var counterChan chan int
func counter() {
	for i := 0; ; i++ { counterChan <- i }
}

func handler(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "%d\n", <-counterChan)
}

func main() {
	counterChan = make(chan int)
	go counter()
	http.HandleFunc("/", handler)
	http.ListenAndServe(":8765", nil)
}

output.txt

$ curl -s http://localhost:8765
0
$ curl -s http://localhost:8765
1
$ curl -s http://localhost:8765
2