Go 2 - Error Handling Proposals

01_existing.go

func CopyFile(src, dst string) error {
	r, err := os.Open(src)
	if err != nil {
		return err
	}
	defer r.Close()

	w, err := os.Create(dst)
	if err != nil {
		return err
	}
	defer w.Close()

	if _, err := io.Copy(w, r); err != nil {
		return err
	}
	if err := w.Close(); err != nil {
		return err
	}
}

02_check.go

func CopyFile(src, dst string) error {
	handle err {
		return fmt.Errorf("copy %s %s: %v", src, dst, err)
	}

	r := check os.Open(src)
	defer r.Close()

	w := check os.Create(dst)
	handle err {
		w.Close()
		os.Remove(dst) // (only if a check fails)
	}

	check io.Copy(w, r)
	check w.Close()
	return nil
}

03_try.go

func CopyFile(src, dst string) (err error) {
	defer func() {
        	if err != nil {
                	err = fmt.Errorf("copy %s %s: %v", src, dst, err)
        	}
	}()

	r := try(os.Open(src))
	defer r.Close()

	w := try(s.Create(dst))
	try(io.Copy(w, r))
	try(w.Close())
	return nil
}