How to get a file by path in C++/WinRT + how to properly handle async calls without crashing?

Question

I'm new to C++ and Windows and trying to write a WinRT/C++ app that can grab a file via path and run it through the built-in Media::Ocr model, but I can't see to even properly get the file into my application as a StorageFile. Here's how I've been trying to do it (to no avail):

runModel()
---------

IAsyncAction runModel() {  
    string _pth = "pic.png";
    hstring pth = to_hstring(_pth);
    StorageFile file = nullptr;
    co_await LoadFileAsync(pth);
 } 

  IAsyncAction LoadFileAsync (hstring pth) {
    StorageFile file = co_await Windows::Storage::StorageFile::GetFileFromPathAsync(pth);
    co_await LoadImageAsync(file);
  }

  IAsyncAction LoadImageAsync(StorageFile const& file) {
      auto stream = co_await file.OpenAsync(Windows::Storage::FileAccessMode::Read);
      auto decoder = co_await BitmapDecoder::CreateAsync(stream);
      auto bitmap = co_await decoder.GetSoftwareBitmapAsync();

      auto imgSource = WriteableBitmap(bitmap.PixelWidth(), bitmap.PixelHeight());
      bitmap.CopyToBuffer(imgSource.PixelBuffer());

      OcrEngine ocrEngine = nullptr;
      ocrEngine = OcrEngine::TryCreateFromUserProfileLanguages();
      auto ocrResult = co_await ocrEngine.RecognizeAsync(bitmap);
      hstring hresult = ocrResult.Text();
      std::cout << hresult.begin();
  }

I'd appreciate any help of the following:

1. Loading the file in as a StorageFile
2. The right way to handle these async calls. I tried to follow https://docs.microsoft.com/en-us/windows/uwp/cpp-and-winrt-apis/concurrency but I couldn't seem to get it to work without this error: !isStaThread()
3. How to properly do the OCR

Thanks!