code: func PutDefault(ch *Changeset, field string, value interface{}, opts ...Option) {
  	options := Options{
  		message: PutDefaultErrorMessage,
  	}
  	options.apply(opts)
  
  	if typ, exist := ch.types[field]; exist {
  		valTyp := reflect.TypeOf(value)
  		if valTyp.ConvertibleTo(typ) {
  			if ch.changes[field] == nil {
  				ch.changes[field] = value
  			}
  			return
  		}
  	}
  
  	msg := strings.Replace(options.message, "{field}", field, 1)
  	AddError(ch, field, msg)
  }
docs: // PutDefault to changeset.