wp post insert with featured image Ajax

<!-- jQuery -->
<script type="text/javascript">
 jQuery('form.portfolio_form').on('submit', function (e) {

          e.preventDefault();

                    var name = jQuery('form.portfolio_form .name').val();
                    var tag = jQuery('form.portfolio_form .tag').val();
                    var link = jQuery('form.portfolio_form .link').val();

                    var formData = new FormData(jQuery('form.portfolio_form')[0]);

          jQuery.ajax({
                            cache: false,
                            processData: false, 
                            contentType:  false,
                            data: formData,
                      type: 'post',
                        url: '/wp-admin/admin-ajax.php',
            success: function (data) {
                            
                            console.log(data);
                            jQuery('.contact_us_form .msg').css('display','block');
                            jQuery('.contact_us_form .msg').html('Portfolio added successfully.');
                        }
                    });
          });
</script>
<!-- function.php wp insert -->
<?php 

add_action( 'wp_ajax_form_submit', 'form_submit' );
add_action( 'wp_ajax_nopriv_form_submit', 'form_submit' );


function form_submit() {

$my_post = array(
  'post_title'    => wp_strip_all_tags( $_POST['name'] ),
  'post_status'   => 'draft',
  'post_author'   => 1,
  'post_type' => 'tie-portfolio'
);

$post_id = wp_insert_post( $my_post );
update_post_meta($post_id, 'wpcf-website-url', $_POST['link']);
update_post_meta($post_id, 'wpcf-tag-line', $_POST['tagline']);

if (!function_exists('wp_generate_attachment_metadata')){
               require_once(ABSPATH . "wp-admin" . '/includes/image.php');
               require_once(ABSPATH . "wp-admin" . '/includes/file.php');
               require_once(ABSPATH . "wp-admin" . '/includes/media.php');
           }

//var_dump(function_exists('wp_generate_attachment_metadata'));
//die('test');
           if (isset($_FILES['image'])) {
      $file = 'image';
              // foreach ($_FILES as $file => $array) {
                   if ($_FILES[$file]['error'] !== UPLOAD_ERR_OK) {
                       return "upload error : " . $_FILES[$file]['error'];

                   }else{ 
                   $attach_id = media_handle_upload( $file, $post_id );
      set_post_thumbnail( $post_id, $attach_id );
      //die('upload');
      }
               //}foreach

           }

 

wp_die();
}

?>
<form name="portfolio_form" action="" method="post" class="portfolio_form" enctype="multipart/form-data">
<input type="hidden" value="form_submit" name="action">
<input type="text" placeholder="Company Name" name="name" class="name">
<input type="text" placeholder="Tag line" name="tagline" class="tag">
<input type="text" placeholder="Website link" name="link" class="link">
<input type="file" name="image" id="image_part" accept="image/x-png, image/gif, image/jpeg">
<img id="image_preview"></img>
</fieldset>


<input type="submit" value="submit" >

</form>