WordPress post password form customization

form.php

// Your page content display by this code 
<?php if ( !post_password_required() ) { ?>
		<?php if (have_posts()) : while (have_posts()) : the_post(); ?>
				<?php the_content(); ?>
		<?php endwhile; endif; ?>
<?php } ?>




// Form customization in same template 
<?php if ( post_password_required() ) : ?> 
<form action="<?php bloginfo('wpurl'); ?>/wp-login.php?action=postpass" method="POST">
<div class="form-group">
			<?php 
					if (isset($_COOKIE['wp-postpass_' . COOKIEHASH]) && $_COOKIE['wp-postpass_' . COOKIEHASH] != $post->post_password) : ?>
						?php 
								$msg = esc_html("Password is Invalid!, please try again.");
								$msg ="<p class='error'><img src='image link'> $msg</p>";
								echo $msg;
						?>
				<?php endif ; ?>
			<input name="post_password" type="password" class="form-control" id="password" placeholder="Enter Your Password Here...">
			<button type="submit" name="Submit" class="btn btn-go btn-block">Go!</button>
		</div>
</form>
<?php endif; ?>