<!doctype html>
<html amp>
<head>
	<meta charset="utf-8">
	<meta name="viewport" content="width=device-width,initial-scale=1,minimum-scale=1,maximum-scale=1,user-scalable=no">
	<?php do_action( 'amp_post_template_head', $this ); ?>

	<style amp-custom>
	<?php $this->load_parts( array( 'style' ) ); ?>
	<?php do_action( 'amp_post_template_css', $this ); ?>
	</style>
</head>
<body>
<?php $this->load_parts( array( 'header-bar' ) ); ?>
<div class="amp-wp-content">
	<h1 class="amp-wp-title"><?php echo wp_kses_data( $this->get( 'post_title' ) ); ?></h1>
	<ul class="amp-wp-meta">
		<?php $this->load_parts( apply_filters( 'amp_post_template_meta_parts', array( 'meta-author', 'meta-time', 'meta-taxonomy' ) ) ); ?>
	</ul>
	<?php echo $this->get( 'post_amp_content' ); // amphtml content; no kses ?>
</div>
<?php do_action( 'amp_post_template_footer', $this ); ?>
</body>
</html>

<!doctype html>
<html amp <?php language_attributes(); ?>>
<head>
	<meta charset="utf-8">
	<meta name="viewport" content="width=device-width,initial-scale=1,minimum-scale=1,maximum-scale=1,user-scalable=no">
	<?php do_action( 'amp_post_template_head', $this ); ?>

	<style amp-custom>
	<?php $this->load_parts( array( 'style' ) ); ?>
	<?php do_action( 'amp_post_template_css', $this ); ?>
	</style>
</head>
<body>
<?php $this->load_parts( array( 'header-bar' ) ); ?>
<div class="amp-wp-content">
	<h1 class="amp-wp-title"><?php echo wp_kses_data( $this->get( 'post_title' ) ); ?></h1>
	<ul class="amp-wp-meta">
		<?php $this->load_parts( apply_filters( 'amp_post_template_meta_parts', array( 'meta-author', 'meta-time', 'meta-taxonomy' ) ) ); ?>
	</ul>
	<?php echo $this->get( 'post_amp_content' ); // amphtml content; no kses ?>
</div>
<?php do_action( 'amp_post_template_footer', $this ); ?>
</body>
</html>

Add lang to `html` tag
Add lang to `html` tag

h/t shivampaw
