src/errors/example_test.go

// Copyright 2012 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 errors_test

import (
	"errors"
	"fmt"
	"os"
	"time"
)

// MyError is an error implementation that includes a time and message.
type MyError struct {
	When time.Time
	What string
}

func (e MyError) Error() string {
	return fmt.Sprintf("%v: %v", e.When, e.What)
}

func oops() error {
	return MyError{
		time.Date(1989, 3, 15, 22, 30, 0, 0, time.UTC),
		"the file system has gone away",
	}
}

func Example() {
	if err := oops(); err != nil {
		fmt.Println(err)
	}
	// Output: 1989-03-15 22:30:00 +0000 UTC: the file system has gone away
}

func ExampleAs() {
	if _, err := os.Open("non-existing"); err != nil {
		var pathError *os.PathError
		if errors.As(err, &pathError) {
			fmt.Println("Failed at path:", pathError.Path)
		} else {
			fmt.Println(err)
		}
	}

	// Output:
	// Failed at path: non-existing
}