getInitialProps does not work with async function

I have file in this path ./pages/blog/[id]/[title].js and here are the codes that I have written :

import React from 'react';
import PropTypes from 'prop-types';
import fetch from 'isomorphic-unfetch';
import BASE_URL from '../../../BaseURL';


const BlogSinglePage = props => {
  console.log(props.post);//undefined
  console.log(props);//{}
 return (
   <div></div>
 );
};

BlogSinglePage.propTypes = {
  post: PropTypes.object
};

BlogSinglePage.getInitialProps = async ({ query }) => {
    const res = await fetch(`${BASE_URL}/api/post/${query.id}`);
    const post = await res.json();
    return { post };
};

export default BlogSinglePage;

my problem is when getInitialProps is an async function , BlogSinglePage 's props is empty but whenever getInitialProps is not an async function , everything works and props is not empty

I have followed the code in Implement the Post Page line by line but it's not working for me