cannot parse string null about carbon

[gouguoyin]

Supported since v2.3.10

type Person struct {
  Birthday1 carbon.Carbon 
  Birthday2 carbon.Carbon
}
str := `{
  "birthday1":"",
  "birthday2":null
}`
var person Person
unmarshalErr := json.Unmarshal([]byte(str), &person)
fmt.Println(unmarshalErr) // nil
fmt.Println(person.Birthday1.String()) // empty string
fmt.Println(person.Birthday2.String()) // empty string

[gouguoyin]

{"field1":null,"field2":null} -> {"field1":"","field2":""}

[a8ss]

The responses of some APIs are null, and I have no control over them.