There is no go back button option in hikashop. However, HikaShop integrates with the breadcrumb module of joomla. So, you could display that breadcrumb module and it would display the tree of categories on the product page. For example, if you look at our demo website on that page
www.demo.hikashop.com/index.php?option=c...y_pathway=11&lang=en
you can see the breadcrumb module displaying the categories above the product page.
Alternatively, you can also edit the file show of the view product and add such code:
<a href="#" onclick="history.back();return false;">Go back</a>
However, that will return to the previous page which might not be the page where you have the products of the same category (for example, if you access the product page via a link on this forum, pressing that go back button would make you return on that forum, like the back button of your browser).