Iterate Flux and concat with Mono in Spring Boot

I do have a fetchEmployment() method which does successfully fetch the records and I am iterating over it to fetch the Mono object based on the worker id which successfully returns the object but I am not able to create the final Flux which should consist of WorkerDTO (list of WorkerDTO for normal Spring Boot application) but it returns the empty object i.e [].

@Override
public Flux<WorkerDTO> method() {
    Flux<EmployeeDTO> employmentDTOFlux = fetchEmployment();
    Flux<WorkerDTO> workerDTOFlux = Flux.empty();

    employmentDTOFlux.flatMap(employmentDTO -> {
        Mono<WorkerDTO> worker = workerService.findWorkerById(employmentDTO.getWorkerId());
        return Flux.concat(workerDTOFlux, Flux.from(worker));
    });

    return workerDTOFlux;
}

The following is simpler and should work as intended:

@Override
public Flux<WorkerDTO> method() {
    return fetchEmployment().flatMap(employmentDTO -> {
        workerService.findWorkerById(employmentDTO.getWorkerId());
    });
}

I think you can rewrite this as something as simple as:

return fetchEmployment()
       .map(EmployeeDTO::getWorkerId)
       .flatMap(workerService::findWorkerById);