go web server don't show html pages (show html code)

[SergeyVlasov]

What version of Go are you using (go version)?

$ go version
1.14

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

xubuntu 18.04

go env Output

$ go env
export PATH=$PATH:/usr/local/go/bin

What did you do?

I write a simple web server by golang. I use gorilla package and i have a problem to show html body of web page. I have an html code instead of web page/ I tried mozilla and chrome (same result)
package main
import (
"html/template"
"net/http"
"github.com/gorilla/mux"
)
func main() {
router := mux.NewRouter()
router.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
tmpl, _ := template.ParseFiles("index.html")
tmpl.Execute(w, nil)
})
http.Handle("/", router)
http.ListenAndServe(":8181", nil)
}

What did you expect to see?

blabla bla bla bla bla bla bla bla bla bla bla

What did you see instead?

I see raw html code:
....

<title>Title</title>

blabla bla bla bla bla bla bla bla bla bla bla

[SergeyVlasov]

I solved problem:
w.Header().Set("Content-Type", "text/html") before execute tmpl

[dmitshur]

Setting the Content-Type header explicitly makes it so that browsers (and the HTTP server) don't have to guess what the content type is. Guessing is hard when the content is very short. Glad you figured this out.

Closing since this isn't a bug in the Go project.