Hi,
We have used below code to open the google map app from click of button on HTML webresource.
<body>
<div id="preloader">
<div id="status"> </div>
</div>
<div>
<a href="comgooglemaps://?saddr=40.20265,-74.79564&daddr=39.68158280659287,-79.42134655761728&directionsmode=driving&zoom=15">
<button>open Google map</button>
</a>
</div>
</body>
Please let us know if you are able to replicate and have solution for the same.
Thanks
Balasaheb