err.go

package main

import (
	"errors"
	"fmt"

	multierror "github.com/hashicorp/go-multierror"
)

func main() {
	a, err := f()
	fmt.Printf("(1) err: %+v\n", err)
	fmt.Printf("(1) err: %p\n", err)
	fmt.Printf("(1) err != nil: %v\n", err != nil)
	b, err := a.g()
	fmt.Printf("(2) err: %+v\n", err)
	fmt.Printf("(2) err: %p\n", err)
	fmt.Printf("(2) err != nil: %v\n", err != nil)
	fmt.Println(b)
}

type F struct{}

func f() (*F, error) {
	return &F{}, errors.New("oops")
}

type G struct{}

func (*F) g() (*G, *multierror.Error) {
	return &G{}, nil
}

output

$ go version
go version go1.10 linux/amd64

$ go run err.go
(1) err: "oops"
(1) err: oops
(1) err: 0xc42000e1e0
(1) err != nil: true
(2) err: <nil>
(2) err: <nil>
(2) err: 0x0
(2) err != nil: true
&{}



👇👇👇 ???????????????????????????????? 👇👇👇

(2) err != nil: true

👆👆👆 ???????????????????????????????? 👆👆👆