Golang を使用して JSON 文字列内の重複属性を検出するにはどうすればよいですか?

func check(d *json.Decoder, path []string, dup func(path []string) error) error {
    // Handle token and delimeters
    t, err := d.Token()
    if err != nil {
        return err
    }

    delim, ok := t.(json.Delim)

    // Skip scaler types
    if !ok {
        return nil
    }

    switch delim {
    case '{':
        // Initialize map for keys and avoid duplicates
        keys := make(map[string]bool)

        for d.More() {
            key := t.(string)

            if keys[key] {
                return dup(append(path, key))
            }

            keys[key] = true

            if err := check(d, append(path, key), dup); err != nil {
                return err
            }
        }
    case '[':
        i := 0
        for d.More() {
            if err := check(d, append(path, strconv.Itoa(i)), dup); err != nil {
                return err
            }
            i++
        }
    }
    return nil
}

data := `{"a": "b", "a":true,"c":["field_3 string 1","field3 string2"], "d": {"e": 1, "e": 2}}`

if err := check(json.NewDecoder(strings.NewReader(data)), nil, printDup); err != nil {
    log.Fatal(err)
}

Duplicate a
Duplicate d/e

func dupErr(path []string) error {
    return ErrDuplicate
}