We are building API's for our mobile applications and prefer keeping API version in url such as "app.com/v1/endpoint". This way we could keep running old applications(not updated by user) without any issue and pushing updates to appstores with new API url for new installs.
We are also following this method in our new API generation tool API Plug too. Our users could generate their API versions on fly and download all versions such as api/v1, api/v2 and upload to their servers.