example.pseudo.go

package main

import "os"

type RefcountedFile proxy[*os.File] struct {
    f *os.File
    refcount int
}

func (f *RefcountedFile) __deref() *os.File {
    return f.f
}

func (f *RefcountedFile) add_ref() RefcountedFile {
    refcount++ // should be done atomically; this is just an example
    return f
}

func (f *RefcountedFile) del_ref() {
    refcount-- // should be done atomically; this is just an example
    if refcount <= 0 {
        f.f.Close()
    }
}

func some_routine(rf RefcountedFile) {
    defer rf.del_ref()
    buf := make([]byte, 4096) 
    n, err := rf.Read(buf)
    // ...
}

func main() {
    f, err := os.Open("some_file")
    if err != nil {
        // do something here
        return
    }
    rf := &RefcountedFile { f, 1 }
    defer rf.del_ref()
    go some_routine(rf.add_ref())
}