[BUG] [Go] Json Unmarshal int bigger then int64

Created by: danijeel

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• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
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Description

in the go generator, trying to unMarshal big int values, get overflow on int64

package main

import (
	"encoding/json"
	"fmt"

	"github.com/danijeel/bigintexample/openapi"
)

func main() {
	jsonSrc := []byte(`{
		"id": 162259276829213363391578010288126,
		"name": "test"
	}`)
	var myJson openapi.Category
	json.Unmarshal(jsonSrc, &myJson)
	fmt.Printf("%d\n", myJson.Id)
	// output: 824634459072
	// expects: 162259276829213363391578010288126
}

Full example can be seen here: https://github.com/danijeel/bigintexample/blob/main/main.go

openapi-generator version

5.2.1

OpenAPI declaration file content or url

The openapi example specification is based on the petstore example https://github.com/danijeel/bigintexample/blob/eb590428c496e152ec32ff30a6464b2849b74a7b/openapi.yml

Generation Details

Steps to reproduce

Related issues/PRs

Suggest a fix

In the branch patch-big-int I replaced the int64 attribute with custom type BigInt in the category model

https://github.com/danijeel/bigintexample/commit/97dde59dd7b6ec4aa136431de31268dda248bb74