How to parse non standard time format from json

Question

lets say i have the following json

{
    name: \"John\",
    birth_date: \"1996-10-07\"
}

and i want to decode it into the following struct

Answer 1

That's a case when you need to implement custom marshal and unmarshal functions.

UnmarshalJSON(b []byte) error { ... }

MarshalJSON() ([]byte, error) { ... }

By following the example in the Golang documentation of json package you get something like:

// First create a type alias
type JsonBirthDate time.Time

// Add that to your struct
type Person struct {
    Name string `json:"name"`
    BirthDate JsonBirthDate `json:"birth_date"`
}

// Implement Marshaler and Unmarshaler interface
func (j *JsonBirthDate) UnmarshalJSON(b []byte) error {
    s := strings.Trim(string(b), "\"")
    t, err := time.Parse("2006-01-02", s)
    if err != nil {
        return err
    }
    *j = JsonBirthDate(t)
    return nil
}
    
func (j JsonBirthDate) MarshalJSON() ([]byte, error) {
    return json.Marshal(j)
}

// Maybe a Format function for printing your date
func (j JsonBirthDate) Format(s string) string {
    t := time.Time(j)
    return t.Format(s)
}