- Return io.ErrUnexpectedEOF when HTTP response is truncated
This prevents silent data corruption from incomplete reads
- Simplify errgroup error handling by using g.Wait() error directly
Remove redundant task.err field and manual error aggregation loop
- Define minReadConcurrency constant instead of magic number 4
Improves code readability and maintainability
Note: Context propagation to startCaching() is intentionally NOT changed.
The downloaded chunk is a shared resource that may be used by multiple
readers. Using context.Background() ensures the download completes even
if one reader cancels, preventing data loss for other waiting readers.