[BUG][GO] AnyOf causes compilation error for Go

[deliveroo-andreik]

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

The generator produces broken code for anyOf

openapi-generator version

v5.2.1

OpenAPI declaration file content or url

Generation Details

generate
--global-property models
--global-property modelDocs=false
--additional-properties sourceFolder=dto,useOneOfDiscriminatorLookup=true
--model-package dto
--package-name dto
-i /local/docs/openapi.yaml
--generate-alias-as-model
-g go
-o /local/internal/server/rest

func (dst *WebhookEvent) UnmarshalJSON(data []byte) error {
	var err error
	// use discriminator value to speed up the lookup
	var jsonDict map[string]interface{}
	err := json.Unmarshal(data, &jsonDict) // <---- compilation error as err already declared in var
	if err != nil {
		return fmt.Errorf("Failed to unmarshal JSON into map for the discrimintor lookup.")
	}
}

Steps to reproduce

Related issues/PRs

Suggest a fix

fix the template and remove unnecessary colon

[andrewkav]

fixed in #10431