[BUG] [go-server] GET Query enum incorrectly cast

Created by: kellrott

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?
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Description

When generating the query.Get commands for the go-server api controller the code incorrectly assumes that the results of query.get (which is a string) can be passed directly to the interface, which may be a subtype of string, ie something defined by type MyEnum string.

openapi-generator version

v5.3.1

OpenAPI declaration file content or url


openapi: 3.0.1

info:
  title: minimal example
  version: "0.1"

servers:
- url: /

paths:
  /list:
    get:
      operationId: DoStuff
      parameters:
      - name: state
        in: query
        schema:
          $ref: '#/components/schemas/myEnum'
      responses:
        200:
          description: ""
          content:
            application/json:
              schema:
                type: string

components:
  schemas:
    myEnum:
      type: string
      default: ENUM_1
      enum:
      - ENUM_1
      - ENUM_2
      - ENUM_3
      - ENUM_4

Generation Details

java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -i test.yaml -g go-server -o tmp

Steps to reproduce

Go to generated code directory, run the command go run ./main.go. The compiler should report

go/api_default.go:66:44: cannot use stateParam (type string) as type MyEnum in argument to c.service.DoStuff

Related issues/PRs

Suggest a fix

In modules/openapi-generator/src/main/resources/go-server/controller-api.mustache, line 136:

-       {{paramName}}Param := {{#isArray}}strings.Split({{/isArray}}query.Get("{{baseName}}"){{#isArray}}, ","){{/isArray}}
+       {{paramName}}Param := {{^isString}}{{dataType}}( {{/isString}}{{#isArray}}strings.Split({{/isArray}}query.Get("{{baseName}}"){{#isArray}}, ","){{/isArray}}{{^isString}} ){{/isString}}

This will change the output from

	stateParam := query.Get("state")
	result, err := c.service.DoStuff(r.Context(), stateParam)

	stateParam := MyEnum( query.Get("state") )
	result, err := c.service.DoStuff(r.Context(), stateParam)

wrapping the query.Get call in a conversion to correct the variable type if it is not a string.