rxjs 6.6.7 and ajax never returns on CORS error

[camer314]

I am trying to make an ajax request from localhost to localhost and am being reject by cors however my subscription never completes, it just hangs. Is this a known issue?

For example, this is my implementation of firstValueFrom (given it is not available in 6) and none of these exit points are hit, the request goes into the void and never either completes or fails:

export async function firstValueFrom(request: Observable<AjaxRequest>) : Promise<any> {

    var p = new Promise((resolve, reject) => {
        try {
            var s = request.subscribe( (v) => {
                s.unsubscribe();
                resolve(v);
            },
            (e) => {
                reject(e);
            },
            () => {
                console.log('complete');
            });
        }
        catch(e) {
            reject(e);
        }
    });

    var result = await p;
    console.log(result);
    return result;
}

The accompanying console message, letting me know the request failed is:

Access to fetch at 'http://localhost:8888/api/terminals/' from origin 'http://localhost:3000' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource

request.js:150 POST http://localhost:8888/api/terminals/ net::ERR_FAILED