github.com/zserge/lorca
<input type="text" name="MACADD" style="height:20px; width:210px">
<input type="submit" value="submit" onclick="JSBINDFUNC(MACADD)">

JSBINDFUNCstringMACADDJSBINDFUNC

However, I'm coming back with the err 

exception":{"type":"string","value":"json: cannot unmarshal object into Go value of type string"}

objectstring

More complete snip:

package main

import (
    "fmt"
    "log"
    "net/url"

    "github.com/zserge/lorca"
)

func main() {
    ui, err := lorca.New("data:text/html,"+url.PathEscape(`
        <html>
                <form action="/action_page.php">
                    MAC Address:<br>
                    <input type="text" name="MACADD" style="height:20px; width:210px">
                    <input type="submit" value="Submit" onclick="JSBINDFUNC(MACADD)">
                </form> 
            </body>
        </html>
        `), "", 480, 320)
    if err != nil {
        log.Fatal(err)
    }
    //ui.Bind implemented @ https://github.com/zserge/lorca/blob/master/ui.go#L110
    ui.Bind("JSBINDFUNC", func(MAC string) {
        fmt.Println(MAC)
        return
    })
    defer ui.Close()
    <-ui.Done()
}