omissis/go-jsonschema

package types

import (
    "errors"
    "fmt"
    "strings"
    "time"
)

var ErrDateNotJSONString = errors.New("cannot parse non-string value as a date")

type SerializableDate struct {
    time.Time
}

func (date SerializableDate) MarshalJSON() ([]byte, error) {
    return []byte("\"" + date.Format(time.DateOnly) + "\""), nil
}

func (date *SerializableDate) UnmarshalJSON(data []byte) error {
    stringifiedData := string(data)
    if stringifiedData == "null" {
        return nil
    }

    if !strings.HasPrefix(stringifiedData, "\"") || !strings.HasSuffix(stringifiedData, "\"") {
        return ErrDateNotJSONString
    }

    dataWithoutQuotes := stringifiedData[1 : len(stringifiedData)-1]

    parsedDate, err := time.Parse(time.DateOnly, dataWithoutQuotes)
    if err != nil {
        return fmt.Errorf("unable to parse date from JSON: %w", err)
    }

    date.Time = parsedDate

    return nil
}