index.go

package main

import (
  "fmt"
  "syscall/js"
  "strconv"
)

func main() {
  num1 := js.Global().Get("document").
    Call("querySelector", "#num1").
    Get("value").
    String()
  i, _ := strconv.Atoi(num1)
  fmt.Println(i)
  num2 := js.Global().Get("document").
    Call("querySelector", "#num2").
    Get("value").
    String()
  j, _ := strconv.Atoi(num2)
  js.Global().Get("document").
    Call("querySelector", "#res").
    Set("value", i + j)
}