[Golang][client] Non-test files should not end in _test.go

[grokify]

Description

Go client generator will create model files that end in _test.go when a definition / schema name ends in Test, _Test, or _test. These files are unreachable and not compiled in Go per the following:

When compiling packages, build ignores files that end in '_test.go'.

Ref: https://godoc.org/github.com/golang/go/src/cmd/go#hdr-Test_packages

The client generator should modify the filename when this is encountered.

openapi-generator version

3.0.3

OpenAPI declaration file content or url

https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/test/resources/2_0/petstore-with-fake-endpoints-models-for-testing.yaml

Command line used for generation

$ bin/go-petstore.sh

Steps to reproduce

Create a program that attempts to use the following generated structs which are created by the spec and command above.

Definition	Struct Name	Filename
ArrayTest	ArrayTest	model_array_test.go
Enum_Test	EnumTest	model_enum_test.go
format_test	FormatTest	model_format_test.go
MapTest	MapTest	model_map_test.go

Related issues/PRs

#449

Suggest a fix/enhancement

Rename the files with an alternate suffix like _test_.go for model_array_test_.go similar to toParamName.