DoTheThing 函数内 err 不是同一个
````go
package main

import (
"errors"
"fmt"
)

var ErrDidNotWork = errors.New("did not work")

func DoTheThing(reallyDoIt bool) (err error) {
fmt.Println("err:",&err)
if reallyDoIt {
result, err := tryTheThing()
if err != nil || result != "it worked" {
err = ErrDidNotWork
}
fmt.Println("err:",&err)
}
return err
}

func tryTheThing() (string,error) {
return "",ErrDidNotWork
}

func main() {
fmt.Println(DoTheThing(true))
fmt.Println(DoTheThing(false))
}
````