golang null field

package main

import (
	"encoding/json"
	"fmt"
)

type amenity struct {
	Category string `json:"category"`
	Name     string `json:"name"`
}

func main() {
	strA := []byte(`{
		"category": "Comida / Bebida",
		"name": "Restaurante Privado"
	}`)
	ameniyA := amenity{}
	json.Unmarshal(strA, &ameniyA)
	fmt.Printf("Com valor:\n%+v\n\n", ameniyA)

	// -------------------------------------------

	strB := []byte(`{
		"category": null,
		"name": "Restaurante Privado"
	}`)
	ameniyB := amenity{}
	json.Unmarshal(strB, &ameniyB)
	fmt.Printf("Com null:\n%+v\n\n", ameniyB)

	// -------------------------------------------

	strC := []byte(`{
		"category": undefined,
		"name": "Restaurante Privado"
	}`)
	ameniyC := amenity{}
	json.Unmarshal(strC, &ameniyC)
	fmt.Printf("Com undefined:\n%+v\n\n", ameniyC)

	// -------------------------------------------

	strD := []byte(`{
		"name": "Restaurante Privado"
	}`)
	ameniyD := amenity{}
	json.Unmarshal(strD, &ameniyD)
	fmt.Printf("Sem o field 'category':\n%+v\n\n", ameniyD)
}