Code Snippet - https://solusipress.com/menyisipkan-script-google-atau-pihak-ketiga-lainnya-pada-wordpress/

snippet-1.php

<?php
add_action( 'wp_head', 'solusipress_ga_script', 0 );
function solusipress_ga_script()
{ ?>
<!-- Global site tag (gtag.js) - Google Analytics -->
<script async src="https://www.googletagmanager.com/gtag/js?id=UA-xxxxxxxxx-1"></script>
<script>
  window.dataLayer = window.dataLayer || [];
  function gtag(){dataLayer.push(arguments);}
  gtag('js', new Date());
  gtag('config', 'UA-xxxxxxxxx-1');
</script>	
<?php }