Method to make callouts handling PATCH request

callout method.cls

/*********************************************************************************
		@description 	: method to make https callouts
		@param 			: url, method, body , headers
		@return 		: HttpResponse
**********************************************************************************/
public static HttpResponse makeCallout(String url, String method, String body, Map<String,String> headers){
	HttpRequest req = new HttpRequest();
	HTTPResponse res = new HTTPResponse();
	Http http = new Http();

	//for patch
	if(method == 'PATCH'){
		req.setMethod('POST');
		url += '?_HttpMethod=PATCH';
	}else{
		req.setMethod(method);
	}

	req.setEndpoint(url);

	if(String.isNotBlank(body)){
		req.setBody(body);
	}
	if(headers != null){
		for(String key : headers.keySet()){
			req.setHeader(key, headers.get(key));
		}
	}
	res = http.send(req);
	return res;
}