When generating w -t ...resource/go-server different results then w/o

In model_* files generated by the openapi-generator-cli-5.3.0.jar w/o specifying a template set w -t I find AssertErrorRequired functions. When I clone the go-server resources and point -t to them these functions are not in the model file.

/ AssertRecurseErrorRequired recursively checks if required fields are not zero-ed in a nested slice.
// Accepts only nested slice of Error (e.g. [][]Error), otherwise ErrTypeAssertionError is thrown.
func AssertRecurseErrorRequired(objSlice interface{}) error {

I was hoping to make small modifications to the templates, but I have lost functionality on templates that have not been modified. My modified main generates as expected.

Additionally, I could not find the string "recursively checks" from the embedded comment anywhere in the openapi-generator repository, regardless of the version I inspected.

Reproduce generation with openapi-generator-cli-5.3.0.jar both with and without -t, using the go-server resources and the model_* outputs described here. Compare the default and cloned templates, then search the repository for AssertRecurseErrorRequired and its embedded comment. Done means the source of the lost function is identified and the behavior is corrected or clearly documented.