How to use an object sent by JS in gopherjs

objtest.go

package main

//go:generate gopherjs build --minify

import (
	"crypto/sha256"

	"github.com/gopherjs/gopherjs/js"
)

func main() {
	js.Module.Get("exports").Set("hashobj", hashobj)
}

func hashobj(obj map[string]interface{}) []byte {
	h := sha256.New()
	for _, k := range []string{"name", "address", "city"} {
		if s, ok := obj[k]; ok {
			switch st := s.(type) {
			case string:
				h.Write([]byte(st))
			case []byte:
				h.Write(st)
			default:
				// ignore types we don't expect
			}
		}
	}
	return h.Sum(nil)
}