package main
import (
"errors
"fmt"
)
var errDo = errors.New("err do")
func do() error {
return fmt.Errorf(" %w", errDo)
}
func main()[{
if err := do(); errors.Is(err, errDo) {
if err == errDo {
fmt.Println("err == errDo")
}else{
fmt.Println("err is errDo")
}
}else{
fmt.Println("err is not errDo")
}
}