// Copyright 2019 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package xerrors_test import ( "fmt" "golang.org/x/xerrors" ) type MyError2 struct { Message string frame xerrors.Frame } func (m *MyError2) Error() string { return m.Message } func (m *MyError2) Format(f fmt.State, c rune) { // implements fmt.Formatter xerrors.FormatError(m, f, c) } func (m *MyError2) FormatError(p xerrors.Printer) error { // implements xerrors.Formatter p.Print(m.Message) if p.Detail() { m.frame.Format(p) } return nil } func ExampleFormatError() { err := &MyError2{Message: "oops", frame: xerrors.Caller(1)} fmt.Printf("%v\n", err) fmt.Println() fmt.Printf("%+v\n", err) }