- Fix handleConnection to use addr parameter for direct upstream map
lookup instead of always selecting the first upstream
- Add Server.Stop() for graceful shutdown with listener closing, UDP
server cleanup, health checker termination, and goroutine joining
- Add shutdownStream() to App and call it in SIGTERM/SIGQUIT/SIGUSR2
signal handlers to prevent goroutine and port leaks on shutdown
Apply modern Go patterns across the codebase:
- Replace `interface{}` with `any` (Go 1.18+)
- Use `for range n` instead of `for i := 0; i < n; i++` (Go 1.22+)
- Replace `sort.Slice` with `slices.Sort` from slices package
- Simplify sync.WaitGroup patterns with errgroup where appropriate
- Add Makefile targets for modernize analyzer
Total: 84 files updated, net reduction of 79 lines
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
