Golang - Defer Modify Returned Value

defer_modify_return_value.go

package main

import (
	"errors"
	"log"
)

func main() {
	err := funWithoutNamedReturn()
	log.Printf("error received from func WITHOUT named return: %+v", err) // the err will be nil

	err = funWithNamedReturn()
	log.Printf("error received from func WITH named return: %+v", err) // the err will not nil
}

func funWithoutNamedReturn() error {
	err := WriteFile()
	if err != nil {
		return err
	}

	defer func() {
		cerr := Close()
		if err == nil {
			err = cerr
		}
	}()

	return err
}

func funWithNamedReturn() (err error) {
	err = WriteFile()
	if err != nil {
		return err
	}

	defer func() {
		cerr := Close()
		if err == nil {
			err = cerr
		}
	}()

	return err
}

func WriteFile() error {
	return nil
}

func Close() error {
	return errors.New("this is coming from function Close()")
}