Function "main" not defined

I am trying to fill two menus separately. But as I can only pass one json to the template, I have to join them in some way. And then extract each menu in a go template.

What is the syntax for doing this? Is it even possible?

package main

import (
	"encoding/json"
	"html/template"
	"os"
)

func main() {
	t := template.Must(template.New("").Parse(templ))

	var m []map[string]interface{}
	if err := json.Unmarshal([]byte(jsondata), &m); err != nil {
		panic(err)
	}

	if err := t.Execute(os.Stdout, m); err != nil {
		panic(err)
	}
}

const templ = `
<html><body>
<ul>
{{ range .main }}
   <li id={{main.menu_id}}> {{main.menu_txt}}</li>
{{ end }}
</ul>
<ul>
{{ range .sub }}
   <li id={{sub.menu_id}}> {{sub.menu_txt}}</li>
{{ end }}
</ul>
</body></html>`

const jsondata = `{
	"main": [{
		"menu_id": "1",
		"menu_txt": "Home"
	}, {
		"menu_id": "2",
		"menu_txt": "Prefs"
	}],
	"sub": [{
		"menu_id": "3",
		"menu_txt": "Test"
	}, {
		"menu_id": "4",
		"menu_txt": "Test2"
	}]
}`

I think I found one solution:

Any other solution?