[swagger 2.0][go server] validate enum function is not generated for 2-dimensional array

Description

This yaml specification generates validateTestItemsEnum() correctly.

definitions:
  TestObject:
    type: object
    properties:
      test:
        type: array
        items:
          type: string
          enum: [AA, BB, CC]

But in case of 2-dimensional array, the validate function is not generated so that build error occurs.

m.validateTest2ItemsEnum undefined (type *TestObject has no field or method validateTest2ItemsEnum)

definitions:
  TestObject:
    type: object
    properties:
      test:
        type: array
        items:
          type: array
          items:
            type: string
            enum: [AA, BB, CC]

Of course, swagger validator does not show any errors on that.

Swagger-codegen version

version: v0.21.0
commit: 7c0fc3ee340f9d99d85573bc54a57e303a639692

Swagger declaration file content or url

Command line used for generation

swagger -q generate server --exclude-main --spec-...

Steps to reproduce

1. Add array of 'string array' in yaml file and define enum values for the 'string array'.
2. Generate code by swagger codegen.
3. codegen is done with success but build error occurs because there's no enum validation function.

Related issues/PRs

Suggest a fix/enhancement

Start with the swagger -q generate server entry point and the Swagger 2.0 Go server generation path, using the two YAML examples in the issue to reproduce the missing validation method. Trace enum validation generation for nested arrays and confirm the generated server builds successfully with a two-dimensional string enum array.