Fetch API Post method is not working

Failed to load http://localhost:9000/api/app/contact: Response to
preflight request doesn’t pass access control check: No
‘Access-Control-Allow-Origin’ header is present on the requested
resource. Origin ‘http://localhost:8080‘ is therefore not allowed
access. If an opaque response serves your needs, set the request’s
mode to ‘no-cors’ to fetch the resource with CORS disabled.