null is a Go library providing an easy to use interface to handle null value or missing key. Type[T any] implements json.Marshaler and json.Unmarshaler . Because of generics it works for any type which can be unmarshalled from/marshalled into JSON.
Marshalling of undefined is an error though.
// define struct with a wrapper type
var s struct {
Key Type[int] `json:"key"`
}
// unmarshal as usual
err := json.Unmarshal(data, &s)
// access value via Value() method, which returns error for null and undefined cases
value, err := s.Key.Value()| JSON | Value | Error |
|---|---|---|
{"key": 42} |
42 |
nil |
{"key": null} |
zero | ErrNull |
{} |
zero | ErrUndefined |
install gotip (until go 1.18 release)
go install golang.org/dl/gotip@latest
gotip download
gotip test -v