fin.go

package main

import "runtime"
import "runtime/debug"

type inner struct {
    data int
}

type outer struct {
    *inner
}

func f1() *inner {
    i := &inner{data: 42}
    runtime.SetFinalizer(i, func(ii *inner) {
        _ = ii
        print("inner finalizer")
    })
    return i
}

func f2() *outer {
    o := &outer{f1()}
    runtime.SetFinalizer(o, func(oo *outer) {
        _ = oo
        print("outer finalizer")
    })
    return o
}

func f3() {
    x := f2()
    print(x.inner.data)
    x = nil
}

func main() {
    f3()
    debug.FreeOSMemory()
    debug.FreeOSMemory()
}