Finalizers

Go Runtime Finalizers Delay Object Reclamation

A Go object with a finalizer is not reclaimed when the garbage collector first determines that it is unreachable. The runtime must retain the object for the finalizer call, and reclamation can occur only after a later collection finds the object unreachable again. That behavior makes runtime.SetFinalizer materially different from ordinary garbage collection. It adds an asynchronous lifecycle phase between loss of application reachability and memory reclamation. Finalization temporarily restores reachability runtime.SetFinalizer(obj, f) associates f with obj. When the collector detects an unreachable object with that association, it clears the association and arranges a call to f(obj).