move graceful shutdown to a single file

pkg/bbgo/graceful_shutdown.go

@@ -0,0 +1,20 @@
+package bbgo
+
+import (
+	"context"
+	"sync"
+)
+
+//go:generate callbackgen -type Graceful
+type Graceful struct {
+	shutdownCallbacks []func(ctx context.Context, wg *sync.WaitGroup)
+}
+
+func (g *Graceful) Shutdown(ctx context.Context) {
+	var wg sync.WaitGroup
+	wg.Add(len(g.shutdownCallbacks))
+
+	go g.EmitShutdown(ctx, &wg)
+
+	wg.Wait()
+}

pkg/bbgo/trader.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"fmt"
 	"reflect"
-	"sync"
 
 	"github.com/pkg/errors"
 	log "github.com/sirupsen/logrus"
@@ -43,20 +42,6 @@ type Validator interface {
 	Validate() error
 }
 
-//go:generate callbackgen -type Graceful
-type Graceful struct {
-	shutdownCallbacks []func(ctx context.Context, wg *sync.WaitGroup)
-}
-
-func (g *Graceful) Shutdown(ctx context.Context) {
-	var wg sync.WaitGroup
-	wg.Add(len(g.shutdownCallbacks))
-
-	go g.EmitShutdown(ctx, &wg)
-
-	wg.Wait()
-}
-
 type Logging interface {
 	EnableLogging()
 	DisableLogging()