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/order.go

@@ -0,0 +1,50 @@
+package shutdown
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/qdm12/golibs/logging"
+)
+
+type Order interface {
+	Append(waves ...Wave)
+	Shutdown(timeout time.Duration, logger logging.Logger) (err error)
+}
+
+type order struct {
+	waves []Wave
+	total int // for logging only
+}
+
+func NewOrder() Order {
+	return &order{}
+}
+
+var ErrIncomplete = errors.New("one or more routines did not terminate gracefully")
+
+func (o *order) Append(waves ...Wave) {
+	o.waves = append(o.waves, waves...)
+}
+
+func (o *order) Shutdown(timeout time.Duration, logger logging.Logger) (err error) {
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	defer cancel()
+
+	total := 0
+	incomplete := 0
+
+	for _, wave := range o.waves {
+		total += wave.size()
+		incomplete += wave.shutdown(ctx, logger)
+	}
+
+	if incomplete == 0 {
+		return nil
+	}
+
+	return fmt.Errorf("%w: %d not terminated on %d routines",
+		ErrIncomplete, incomplete, total)
+}