I want to use goja to add a scripting layer to my software with some success. Yet I struggle to implement a bytes.Buffer accessor. This is the code. I like to use something like d.Field = "foo" or something similar.

package main

import (
    "bytes"
    "fmt"
    "os"

    "github.com/dop251/goja"
)

type document struct {
    Field bytes.Buffer
}

func newDocument() *document {
    d := &document{}
    // I'd like to have this on the javascript side:
    // d.Field.Write([]byte("foo"))
    return d
}

func (d *document) Check() {
    // Goal: should print "foo"
    fmt.Println(`~~> d.Field`, d.Field.String())
}

func main() {
    runtime := goja.New()

    gjNewDoc := func(call goja.FunctionCall) goja.Value {
        return runtime.ToValue(newDocument())
    }
    runtime.Set("newdoc", gjNewDoc)

    _, err := runtime.RunString(`
var d = newdoc();
d.Field = "foo";
d.Check();
`)
    if err != nil {
        fmt.Println(err)
        os.Exit(-1)
    }

}

Any idea how to add data to the filed d.Field? If this is not directly possible: what would be a good workaround?

I have also asked this question on the discussion page of goja, but had no luck with an answer.