Don't use primitives for things like email

gistfile1.go

// An electronic mail address
type email struct {
	s string
}

var invalidEmail = errors.New("invalid email")

func newEmail(s string) (email, error) {
	s = strings.Trim(s, " ")

	if len(s) < 3 {
		return email{}, invalidEmail
	}

	if !strings.Contains(s, "@") {
		return email{}, invalidEmail
	}

	return email{s: s}, nil
}

func (e *email) Scan(src interface{}) error {
	b, ok := src.([]byte)
	if !ok {
		err := errors.New(
			fmt.Sprintf("can't scan email from %#v", src),
		)
		glog.Error(err)
		return err
	}

	email, err := newEmail(string(b))
	if err != nil {
		return err
	}
	e.s = email.s
	return nil
}

func (e email) Value() (driver.Value, error) {
	return driver.Value(e.s), nil
}