Add missing flatMap import
MODIFY
packages/core/src/http.listener.ts
packages/core/src/http.listener.ts
import { Subject, of } from 'rxjs';
-import { catchError, defaultIfEmpty, switchMap, tap } from 'rxjs/operators';
+import { catchError, defaultIfEmpty, switchMap, flatMap, tap } from 'rxjs/operators';
import { combineEffects, combineMiddlewareEffects } from './effects/effects.combiner';
import { Effect, EffectResponse, GroupedEffects } from './effects/effects.interface';
import { Http, HttpRequest, HttpResponse, HttpStatus } from './http.interface';

Add missing flatMap import