[BUG][Go] Default string values of enums are not double quoted

Created by: jlsherrill

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

When trying to generate a Go client binding for pulp (https://docs.pulpproject.org/pulp_rpm/_static/api.json), default values that are strings do not seem to be double quoted:

For example, a generated model for the mentioned spec is:

func NewRpmRpmRemote(name string, url string) *RpmRpmRemote {
        this := RpmRpmRemote{}
        this.Name = name
        this.Url = url
        var policy PolicyEnum = immediate
        this.Policy = &policy
        return &this
}

This fails to compile, and the generated tests fail with:

./model_rpm_rpm_remote.go:86:26: undefined: immediate

I would expect immediate to be wrapped in double quotes:

        var policy PolicyEnum = "immediate"

I suspect that this is related to toDefaultValue() here: https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientCodegen.java#L391-L405

Its either not being called, or is not detecting the string properly. The value mentioned is an enum and from testing with a simplified example, that is the root of the problem

openapi-generator version

6.4.0-SNAPSHOT
2023-02-09T02:46:35Z

OpenAPI declaration file content or url

http://localhost:8080/pulp/api/v3/docs/api.json

i've created a simpler example here: https://gist.github.com/jlsherrill/af376f50ca7692332ab19ce01d88ee11

Generation Details

          docker run --network=host --rm -v ${PWD}:/local openapitools/openapi-generator-cli generate \
           -i http://localhost:8080/pulp/api/v3/docs/api.json \
           -g go \
          -o /local/packages/pulpGoBinding  --skip-validate-spec \
           --git-user-id=user_id --git-repo-id=repo_id \
           --package-name=pulpGoBinding \
           -p enumClassPrefix=true \
           -p structPrefix=true \
           -p disallowAdditionalPropertiesIfNotPresent=true

Steps to reproduce

Generate go bindings with the above command, and then run the resulting tests:

$  go test ./...
./model_patchedrpm_rpm_remote.go:74:26: undefined: immediate
./model_patchedrpm_rpm_remote.go:84:26: undefined: immediate
./model_patchedrpm_uln_remote.go:74:26: undefined: immediate
./model_patchedrpm_uln_remote.go:84:26: undefined: immediate
./model_rpm_rpm_remote.go:76:26: undefined: immediate
./model_rpm_rpm_remote.go:86:26: undefined: immediate
./model_rpm_rpm_remote_response.go:74:26: undefined: immediate
./model_rpm_rpm_remote_response.go:84:26: undefined: immediate
./model_rpm_uln_remote.go:78:26: undefined: immediate
./model_rpm_uln_remote.go:88:26: undefined: immediate
./model_rpm_uln_remote.go:88:26: too many errors

Related issues/PRs

Suggest a fix

Currently working to get a build going to try to debug further.