go/doc/next/6-stdlib/99-minor/runtime/72949.md

When GODEBUG=checkfinalizers=1 is set, the runtime will run diagnostics on each garbage collection cycle to find common issues with how the program might use finalizers and cleanups, such as those described in the GC guide. In this mode, the runtime will also regularly report the finalizer and cleanup queue lengths to stderr to help identify issues with long-running finalizers and/or cleanups.