This is a library for handling errors in Go language.
This package combines Go standard errors package and github.com/pkg/errors.
All funcs from both packages are available.
On top of them, I added some sentinels for common errors I need all the time.
All sentinels are from the same type which contains various information. Whenever a sentinel is used, a StackTrace is also generated.
Here is how to use the errors:
func findme(stuff map[string]string, key string) (string, error) {
if value, found := stuff[key]; found {
return value, nil
}
return "", errors.NotFound.With("key", key)
}
func main() {
var allstuff[string]string
//...
value, err := findme("key1")
if errors.Is(err, errors.NotFound) {
fmt.Fprintf(os.Stderr, "Error: %+v", err)
// This should print the error its wrapped content and a StackTrace.
}
}If you plan to do something with the content of the error, you would try that:
func main() {
var allstuff[string]string
//...
value, err := findme("key1")
if errors.Is(err, errors.NotFound) {
var details *errors.Error
if errors.As(err, &details) {
fmt.Fprintf(os.Stderr, "Could not find %s", details.What)
}
}
}Note: You should not use var details errors.Error, use the pointer version var details *errors.Error instead.
When several errors.Error are chained up, this can be used to extract the ones you want:
func main() {
var allstuff[string]string
//...
value, err := findme("key1")
if errors.Is(err, errors.NotFound) {
details := errors.NotFound.Clone()
if errors.As(err, &details) {
fmt.Fprintf(os.Stderr, "Could not find %s", details.What)
}
}
}To return an HTTP Status as an error, you could do this:
func doit() error {
req, err := http.NewRequest(http.MethodGet, "http://www.acme.org")
if err != nil {
return errors.WithStack(err)
}
httpclient := http.DefaultClient()
res, err := httpclient.Do(req)
if err != nil {
return errors.WithStack(err)
}
if res.StatusCode >= 400 {
return errors.FromHTTPStatusCode(res.StatusCode)
}
return nil
}
func main() {
err := doit()
if (errors.Is(err, errors.HTTPBadRequest)) {
// do something
}
// do something else
}You can chain multiple errors together (See Example):
func doit() error {
// ... some processing
var urlError *url.Error // errors from the net/url package
return errors.WrapErrors(err, errors.NotFound.With("key", "key1"), urlError)
}You can also use a errors.MultiError to collect multiple errors together (See Example):
me := errors.MultiError{}
me.Append(errors.NotFound.With("key", "key1"))
me.Append(errors.NotFound.With("key", "key2"))
fmt.Println(me.AsError())Finally, errors.Error supports JSON serialization:
err := errors.InvalidType.With("bogus")
payload, jerr := json.Marshal(err)
// ...