How can I set a default product variant in my online store?

[Sibrahimi]

Hello,

I have a product with 2 variants. When i click on the product in the collection page, no variant is set by default.

After click in the collection, the URL is www.myshop.com/product/xxxx?variant=

Because there are no variant ID by default in the URL, the product is not available.

I expect to have by defaut this URL  www.myshop.com/product/xxxx?variant=999999999 

How can i setup that ?