why does this not time out?

timeoutserver.go

package main

import (
	"net/http"
	"time"
)

func main() {
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		time.Sleep(10 * time.Second)
		w.Write([]byte("hey"))
	})
	server := http.Server{
		Addr:         ":8000",
		WriteTimeout: 3 * time.Second,
	}
	server.ListenAndServe()
}