login with google always asks user consent

Google login does not require user consent every time. If you're using OAuth2 Login procedure, you should be able to login a second time w/o re-approvals: https://developers.google.com/accounts/docs/OAuth2Login

In some contexts, however, it is possible for auto-approval to become disabled, with the subsequent requirement of user consent on every login.

The first and most common case is if your application explicitly requests Google to prompt for consent everytime. Check if your authorization request (which you may have copied from an example or sample code) includes 'prompt=consent' or the older, non-standard form 'approval_prompt=force'. Removing these parameters (if present), will likely cause auto-approval to start working.

Another situation is if your redirect URL is based on 'localhost' or some other URL that does not belong to the global DNS namespace. In this case, for security reasons, Google sets a cookie on the user's computer, in the accounts.google.com domain, to signal that the user authorized _this_device_ to login to 'foo' on localhost (or local domain); Google will only auto-approve w/o consent a 2nd request if it finds the cookie. The reason is that the meaning of 'localhost' (or local domain, or other URL not built on global DNS namespace) is device-dependent, and allowing the authorization to apply across devices could introduce security risks. So if your company has configured browsers to clear all cookies on exit, and you use a non-absolute URL, you could see your users having to consent everytime. The solution is either to host your endpoint on an Internet-valid hostname (the host doesn't need to be accessible from outside the Intranet, just the hostname needs to be globally valid), or you need to exempt accounts.google.com from the cookie clearing policy.