4同步異步

注意：

goroutinues機制可以方便實現異步處理

在啓動新的goroutinues時，不應該使用原始上下文，必須使用它的只讀副本

	r.GET("/long_async", func(c *gin.Context) {
		// create copy to be used inside the goroutine
		//不能直接用c
		cCp := c.Copy()
		go func() {
			// simulate a long task with time.Sleep(). 5 seconds
			time.Sleep(5 * time.Second)

			// note that you are using the copied context "cCp", IMPORTANT
			log.Println("Done! in path " + cCp.Request.URL.Path)
		}()
		log.Println("主方法")
	})