func (ns *NullString) Scan(value interface{}) error {
	if value == nil {
		ns.String, ns.Valid = "", false
		return nil
	}
	ns.String, ns.Valid = value.(string)
	return nil
}
Scan implements the Scanner interface.
package types
import (
	"database/sql/driver"
	"encoding/json"
	"errors"
	"strconv"
)
const Version = "0.22"
type NullString struct {
	Valid  bool
	String string
}
func (ns *NullString) UnmarshalJSON(b []byte) error {
	if string(b) == "null" {
		ns.Valid = false
		return nil
	}
	var s string
	err := json.Unmarshal(b, &s)
	if err != nil {
		return err
	}
	ns.Valid = true
	ns.String = s
	return nil
}
func (ns NullString) MarshalJSON() ([]byte, error) {
	if !ns.Valid {
		return []byte("null"), nil
	}
	s, err := json.Marshal(ns.String)
	if err != nil {
		return []byte{}, err
	}
	return s, nil
}