structtag

const (
	UndTag = "und"
	// The field must be required(Some or Defined).
	// mutually exclusive to nullish, def, null, und.
	// UndTagValueRequired can be combined with len (there's no point though).
	UndTagValueRequired = "required"
	// The field must be nullish(None, Null, Undefined).
	// mutually exclusive to required, def, null, und.
	// UndTagValueNullish can be combined with len.
	UndTagValueNullish = "nullish"
	// The field is allowed to be Some or Defined.
	// can be combined with null, und or len.
	UndTagValueDef = "def"
	// The field is allowed to be None or Null.
	// can be combined with def, und or len.
	UndTagValueNull = "null"
	// The field is allowed to be None or Undefined.
	// can be combined with def, null or len.
	UndTagValueUnd = "und"
	// Only for elastic types.
	//
	// The value must be formatted as len==n, len>n, len>=n, len<n or len<=n,
	// where n is unsigned integer.
	// The field's length will be evaluated as (length) (comparison operator) (n),
	// e.g. if tag is len>12, field.Len() > 12 must return true.
	//
	// can be combined with other options.
	UndTagValueLen = "len"
	// Only for elastic types.
	//
	// The value must be formatted as values:nonnull.
	//
	// nonnull value means its internal value must not have null.
	UndTagValueValues = "values"
)