As stated in the documentation, you could request features with issue trackers:
You can also request and vote for new Google Cloud features. Unlike issue reports, we don't immediately triage new feature requests. Instead, we wait for a feature to have a handful of stars and, hopefully, comments from several users about how the feature would be useful. So, when it comes to feature requests, it's especially important to vote for an existing request (if one exists) instead of making a duplicate.
As stated in the request at Support statement_timeout for PostgreSQL database flag.
To star an issue, you should follow these steps:
Open the issue.
Click the star icon next to the issue title.
As I can see in the thread, there is a comment stating that the request has been forwarded to the Cloud SQL product team.
If you need further assistance, you can open a Support case.