Display post metadata: “title, category, author, date” with shortcode

If you are outside the loop then you can use to get them by post id, you can play around with these snippet:

shortcode for author’s name:

function author_name_shortcode(){
    global $post;
    $post_id = $post->ID;
    $author = get_the_author($post_id);
    return $author;
}
add_shortcode('post_author','author_name_shortcode');

shortcode for categories name:

function category_name_shortcode(){
    global $post;
    $post_id = $post->ID;
    $catName = "";
    foreach((get_the_category($post_id)) as $category){
        $catName .= $category->name . " ,";
    }
    return $catName;
}
add_shortcode('post_category','category_name_shortcode');