[BUG] Code generation completely skips "string64" parameter

Description

SPEC contains (extract of the relevant parts):

components:
  schemas:
    string64:
      maxLength: 64
      type: string

which is then referenced elsewhere with a simple ref:

    hoststate:
      $ref: '#/components/schemas/string64'

The generator completely skips hoststate, leading to errors at buildtime (go-server):

$ java -jar openapi-generator-cli.jar generate -o server/ -g go-server -i openapi-3.1.yaml
$ cd server
$ go build

go/model_host.go:24:12: undefined: Hoststate
...
... too many errors

---

The generated code also forgets to import "errors" and "io" leading to other build errors that can be easily worked around by manually adding the missing imports (separate issue).

By removing the string64 and directly using "string", the problem goes away, like this:

    hoststate:
      maxLength: 64
      type: string

(leaving only the missing "errors" and "io" imports)

It's painful and less concise though to replace everywhere in the API all references to fixed length types, since they appear many times.

openapi-generator version

using latest stable version, at this time 7.12.0

OpenAPI declaration file content or url

components:
  schemas:
    string64:
      maxLength: 64
      type: string

Generation Details

java -jar openapi-generator-cli.jar generate -o server/ -g go-server -i openapi-3.1.yaml

Steps to reproduce

As per Generation Details and the OpenAPI snippet. Adding any ref to string64 does not work.

Suggest a fix

It should generate the code for all components that reference string64. Currently it silently skips all components that are a $ref to string64.

Start by reproducing the issue with the provided OpenAPI schema and go-server generation command, then inspect the generated go/model_host.go where Hoststate is missing. Trace how the generator handles components referenced through string64; done means the referenced Hoststate model is generated, while the separately reported missing errors and io imports remain out of scope.