Sending signals by closing the channel (#17917)

Signed-off-by: Iceber Gu <[email protected]>

src/cmd/migrate-patch/main.go

@@ -48,20 +48,23 @@ func main() {
 		log.Fatalf("Failed to connect to Database, error: %v\n", err)
 	}
 	defer db.Close()
-	c := make(chan struct{}, 1)
+
+	c := make(chan struct{})
 	go func() {
+		defer close(c)
+
 		err := db.Ping()
 		for ; err != nil; err = db.Ping() {
 			log.Println("Failed to Ping DB, sleep for 1 second.")
 			time.Sleep(1 * time.Second)
 		}
-		c <- struct{}{}
 	}()
 	select {
 	case <-c:
 	case <-time.After(30 * time.Second):
 		log.Fatal("Failed to connect DB after 30 seconds, time out. \n")
 	}
+
 	row := db.QueryRow(pgSQLCheckColStmt)
 	var tblCount, colCount int
 	if err := row.Scan(&tblCount, &colCount); err != nil {

src/core/main.go

@@ -104,14 +104,14 @@ func gracefulShutdown(closing, done chan struct{}, shutdowns ...func()) {
 	signal.Notify(signals, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT)
 	log.Infof("capture system signal %s, to close \"closing\" channel", <-signals)
 	close(closing)
-	shutdownChan := make(chan struct{}, 1)
+	shutdownChan := make(chan struct{})
 	go func() {
+		defer close(shutdownChan)
 		for _, s := range shutdowns {
 			s()
 		}
 		<-done
 		log.Infof("Goroutines exited normally")
-		shutdownChan <- struct{}{}
 	}()
 	select {
 	case <-shutdownChan: