[BUG] [GO] api.mustache template builds a client that does not correctly set header params

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

Go's api.mustache template builds a Go client that adds header params as query params. The bug was introduced in this PR and still exists on the latest main branch.

openapi-generator version

This issue doesn't yet appear to be included in a release (the PR was merged on Nov 19, 2022, and the latest release was on Nov 1, 2022 [v6.2.1]).

That being said, the latest main branch includes this code. I'm using the openapi-generator-cli and docker without specifying a version and seem to be pulling in the changes from main.

OpenAPI declaration file content or url

Example yaml file with headers included:

swagger: "2.0"
info:
  version: 1.0.0
  title: Swagger Petstore
  description: >
    A sample API that uses a petstore as an example
    to demonstrate features in the swagger-2.0 specification
consumes:
  - application/json
produces:
  - application/json
paths:
  /pets:
    get:
      description: Returns all pets from the petstore
      parameters:
        - name: X-Region
          in: header
          type: string
          required: true
      responses:
        "200":
          description: pet response
          schema:
            type: array
            items:
              $ref: "#/definitions/pet"
        default:
          description: unexpected error
          schema:
            $ref: "#/definitions/errorModel"
definitions:
  pet:
    $ref: sample/pet.yaml
  pet-owner:
    $ref: sample/pet-owner.yaml
  errorModel:
    $ref: sample/error.json

Generation Details

I'm using the openapi-generator-cli and docker to generate my Go client.

Steps to reproduce

1. Run openapi-generator-cli with docker on an OpenAPI spec yaml file that includes headers. Pull generated client code into a Go repo.
2. Build requests using the above generated Golang client. Requests will not set header params at all (and instead it appears they will be added to query params).

Related issues/PRs

• Issue referenced here in Stack Overflow
• PR that introduced the bug

Suggest a fix

The fix should be minor - the api.mustache template needs a few lines updated to set headers instead of query params.

Inspect modules/openapi-generator/src/main/resources/go/api.mustache around lines 243-252, then generate a Go client from the header-containing OpenAPI YAML in the issue. Build a request with the generated client and verify that X-Region is sent as a header rather than appearing in query parameters; update the template and confirm the generated behavior.