go - Terminating function execution if a context is cancelled

Question

I have this current function that originally was not context aware.

func (s *Service) ChunkUpload(r *multipart.Reader) error {
    chunk, err := s.parseChunk(r)
    if err != nil {
        return fmt.Errorf("failed parsing chunk %w", err)
    }

    if err := os.MkdirAll(chunk.UploadDir, 02750); err != nil {
        return err
    }

    if err := s.saveChunk(chunk); err != nil {
        return fmt.Errorf("failed saving chunk %w", err)
    }

    return nil
}

I've updated it's method call to now take a context.Context as its first argument. My main goal is to terminate and return the function as soon as the context is cancelled.

My initial implementation was this.

func (s *Service) ChunkUpload(ctx context.Context, r *multipart.Reader) error {
    errCh := make(chan error)

    go func() {
        chunk, err := s.parseChunk(r)
        if err != nil {
            errCh <- fmt.Errorf("failed parsing chunk %w", err)
            return
        }

        if err := os.MkdirAll(chunk.UploadDir, 02750); err != nil {
            errCh <- err
            return
        }

        if err := s.saveChunk(chunk); err != nil {
            errCh <- fmt.Errorf("failed saving chunk %w", err)
            return
        }
    }()

    select {
    case err := <-errCh:
        return err
    case <-ctx.Done():
        return ctx.Err()
    }
}

However, as I thought about the execution of the code I realized that this doesn't achieve my goal. Since all the function's logic is in a separate go routine even if context gets cancelled and I return ChunkUpload early the code within the go routine will continue to execute thus not really making a difference from the original code.

The next though was okay just pass a context to all inner functions like s.parseChunk and s.saveChunk but this option also doesn't seem right as I would need to implement cancellations in each function. What would be the proper way to refactor this original function to be context aware and terminate as soon as a context is cancelled?

Answer 1

Waitting for answers