Making a Simple FileServer with Go and Localhost Refused to Connect

Now I have the following code extracted from a book.

package main

import (
	"net/http"
)

func main() {
	h := http.FileServer(http.Dir("."))
	http.ListenAndServeTLS(":8001", "rui.crt", "rui.key", h)
}

I expect it can list all the file in the folder of main.go but when I browse to:
https://localhost:8001
I can only see:

This site can’t be reached.  
localhost refused to connect.

I use LiteIDE to build and run the program. After <kbd>BuildAndRun</kbd> clicked, the following messages are shown.

F:/Go/bin/go.exe build -i [E:/Users/User/Desktop/codespace_v2.6.6/dev/server_side/golang/go_codespace_v2.1/server]
Success: process exited with code 0.
E:/Users/User/Desktop/codespace_v2.6.6/dev/server_side/golang/go_codespace_v2.1/server/server.exe  [E:/Users/User/Desktop/codespace_v2.6.6/dev/server_side/golang/go_codespace_v2.1/server]
Success: process exited with code 0.

Why and how can I fix it?

your system cannot find the certificate file.:
this error means you need "rui.crt" file alongside with your main binary file.
if you do not have certificate see: https://stackoverflow.com/questions/10175812/how-to-create-a-self-signed-certificate-with-openssl

then copy "server.pem", "server.key" files to your binary(.exe) file directory

and run this sample code (for test):

package main

import (
	"fmt"
	"log"
	"net/http"
)

type server struct {
}

func (s server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	fmt.Fprint(w, "*Hello World\n*")
}

func main() {
	if err := http.ListenAndServeTLS(":443", "server.pem", "server.key", server{}); err != nil {
		log.Fatal(err)
	}
}

then open web page: https://127.0.0.1/
if firewall poped up say yes,
if you see There is a problem with this website’s security certificate. say continue (advance).

output:

*Hello World
*