TL;DR:

Note

• Fix released in package: google_sign_in: ^6.0.0.
• Read the migration notes in the google_sign_in_web README.

Original issue below:

Internal: b/233812803

Internal: b/259309242

Google Sign-In JavaScript Platform Library used by the google_sign_in web plugin will be discontinued on March 31, 2023.

It is being replaced by Google Identity Services

https://github.com/flutter/plugins/blob/b548ae18646d1725a8e1f004c26bf42e4d362aa8/packages/google_sign_in/google_sign_in_web/lib/google_sign_in_web.dart#L24

See also

• [google_sign_in] web implemented uses deprecated APIs #101004