in convert.go [45:55]
func convertMarshal(val reflect.Value) (bool, string, error) {
// Check first for the Marshaler interface
if val.Type().NumMethod() > 0 && val.CanInterface() {
if marshaler, ok := val.Interface().(Marshaler); ok {
ret, err := marshaler.MarshalFlag()
return true, ret, err
}
}
return false, "", nil
}