Access to XMLHttpRequest has been blocked by CORS policy

I've a problem when I try to do PATCH request in an angular 7 web application. In my backend I have:

app.use((req, res, next) => {
res.set({
"Access-Control-Allow-Origin": "*",
"Access-Control-Allow-Methods": "*",
"Access-Control-Allow-Headers": "'Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token'",
});

next();
});


In my frontend service, I've:

patchEntity(ent: any, id) {
let headers = new Headers({ 'Content-Type': '*' });
let options = new RequestOptions({ headers: headers });
return this.http.patch('my_url', ent).map((res: Response) => res.json());
};


The error is:

Access to XMLHttpRequest at 'my_url' from origin 'http://localhost:4200' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: It does not have HTTP ok status.


What can I to do? Thanks.

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