use options instead of opts in error message

core/mapping/unmarshaler.go

@@ -345,7 +345,7 @@ func (u *Unmarshaler) processNamedFieldWithValue(field reflect.StructField, valu
 			options := opts.options()
 			if len(options) > 0 {
 				if !stringx.Contains(options, mapValue.(string)) {
-					return fmt.Errorf(`error: value "%s" for field "%s" is not defined in opts "%v"`,
+					return fmt.Errorf(`error: value "%s" for field "%s" is not defined in options "%v"`,
 						mapValue, key, options)
 				}
 			}