chore: add time sleep in close http server example

Author: appleboy

graceful-shutdown/close/server.go

@@ -7,13 +7,15 @@ import (
 	"net/http"
 	"os"
 	"os/signal"
+	"time"
 
 	"github.com/gin-gonic/gin"
 )
 
 func main() {
 	router := gin.Default()
 	router.GET("/", func(c *gin.Context) {
+		time.Sleep(5 * time.Second)
 		c.String(http.StatusOK, "Welcome Gin Server")
 	})