Exemplo de error handling com go 1.13

error.go

package main

import (
	"errors"
	"fmt"
)

type DBError struct {
	message string
	err     error
}

func (dbErr *DBError) Error() string {
	return dbErr.message
}
func (dbErr *DBError) Wrap(e error) {
	dbErr.err = e
}
func (dbErr *DBError) Unwrap() error {
	return dbErr.err
}

type OtherError string

func (oErr OtherError) Error() string {
	return string(oErr)
}

const (
	ErrPermissionDenied = OtherError("permission denied")
	ErrNotFound         = OtherError("not found")
)

func DoSomething1() *DBError {
	err := &DBError{message: "error doing something"}
	err.Wrap(ErrPermissionDenied)
	return err
}

func DoSomething2() *DBError {
	err := &DBError{message: "error doing something"}
	err.Wrap(ErrNotFound)
	return err
}

func main() {
	err := DoSomething1()

	if errors.Is(err, ErrPermissionDenied) {
		fmt.Println("permission error")
	}
	err = DoSomething2()
	if errors.Is(err, ErrNotFound) {
		fmt.Println("not found error")
	}
}