Maintenance: shutdown order

- Order of threads to shutdown (control then tickers then health etc.)
- Rely on closing channels instead of waitgroups
- Move exit logs from each package to the shutdown package

internal/shutdown/routine.go

@@ -0,0 +1,39 @@
+package shutdown
+
+import (
+	"context"
+	"fmt"
+	"time"
+)
+
+type routine struct {
+	name    string
+	cancel  context.CancelFunc
+	done    <-chan struct{}
+	timeout time.Duration
+}
+
+func newRoutine(name string) (r routine,
+	ctx context.Context, done chan struct{}) {
+	ctx, cancel := context.WithCancel(context.Background())
+	done = make(chan struct{})
+	return routine{
+		name:   name,
+		cancel: cancel,
+		done:   done,
+	}, ctx, done
+}
+
+func (r *routine) shutdown(ctx context.Context) (err error) {
+	ctx, cancel := context.WithTimeout(ctx, r.timeout)
+	defer cancel()
+
+	r.cancel()
+
+	select {
+	case <-r.done:
+		return nil
+	case <-ctx.Done():
+		return fmt.Errorf("for routine %q: %w", r.name, ctx.Err())
+	}
+}