Nuxt/test/fixtures/children/pages/parent/_id.vue

<template>
  <h2>Id={{ id }}</h2>
</template>

<script>
export default {
  async asyncData({ route }) {
    const asyncData = {};

    await new Promise((resolve, reject) => {
      setTimeout(() => {
        asyncData.id = route.params.id;
        resolve();
      }, 50)
    });

    return asyncData;
  }
}
</script>