go语言 自定义 error

package mainimport ("errors""fmt")type data struct{}func (this *data) Error() string { return "" }func bad() bool {return true}//自定义错误返回函数func test() error {var p *data = nilif bad() {return p}return nil}//只是返回错误非空func test1() error {var val error = errors.New("XXX")return val}func main() {var e error = test()if e == nil {fmt.Println("e is nil")} else {fmt.Println("e is not nil")}var e1 error = test1()if e1 == nil {fmt.Println("e1 is nil")} else {fmt.Println("e1 is not nil")fmt.Println(e1.Error())}}