null

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.

Usage

// 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

Build and test

install gotip (until go 1.18 release)

go install golang.org/dl/gotip@latest
gotip download
gotip test -v