Add iso-3166-2 (#788)

Author: erma07

baked_in.go

@@ -189,6 +189,7 @@ var (
 		"iso3166_1_alpha2":              isIso3166Alpha2,
 		"iso3166_1_alpha3":              isIso3166Alpha3,
 		"iso3166_1_alpha_numeric":       isIso3166AlphaNumeric,
+		"iso3166_2":              	 isIso31662,
 		"bcp47_language_tag":            isBCP47LanguageTag,
 		"postcode_iso3166_alpha2":       isPostcodeByIso3166Alpha2,
 		"postcode_iso3166_alpha2_field": isPostcodeByIso3166Alpha2Field,
@@ -2345,6 +2346,12 @@ func isIso3166AlphaNumeric(fl FieldLevel) bool {
 	return iso3166_1_alpha_numeric[code]
 }
 
+// isIso31662 is the validation function for validating if the current field's value is a valid iso3166-2 code.
+func isIso31662(fl FieldLevel) bool {
+	val := fl.Field().String()
+	return iso3166_2[val]
+}
+
 // isBCP47LanguageTag is the validation function for validating if the current field's value is a valid BCP 47 language tag, as parsed by language.Parse
 func isBCP47LanguageTag(fl FieldLevel) bool {
 	field := fl.Field()