how to concatenate a json key in vuejs coming from laravel API

I need to concatenate a json key for displaying the contents based on the current language selected. In API I am getting the response and current language selected. The response is like below

{
  lang : "en"
  heading_ar: "قابل وتناول واستمتع بالاختبار الحقيقي"
  heading_en: "Meet, Eat & Enjoy the true test"
  description_ar: "<p>هناك حقيقة مثبتة منذ زمن طويل وهي أن المحتوى المقروء لصفحة</p>"
  description_en: "<p>It is a long established fact that a</p>"
  id: 1
}

in template I should display the contents. But I cannot able to concatenate lang in heading . I tried different ways but nothing is working.

<template>
<h1 class="banner-title">{{banner.home.heading_+banner.home.lang}}</h1>
</template>

thank you