How to send ProgressNotification to clients

[sotex]

Refer to the example: examples/sampling_http_server/main.go, create an MCP service, add the following processing, but it doesn't seem to work, the client is not receiving progress notifications.

func downloadHandler(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
	url, err := request.RequireString("url")
	if err != nil {
		return mcp.NewToolResultError(err.Error()), nil
	}
	fmt.Println("Simulation download:", url)
	total := 100.0
	session := server.ClientSessionFromContext(ctx)
	session.(server.SessionWithStreamableHTTPConfig).UpgradeToSSEWhenReceiveNotification()
	for i := 0; i < 100; i++ {
		msg := fmt.Sprintf("Download progress: %d%%", i+1)
		progress := mcp.NewProgressNotification(request.Params.Meta.ProgressToken, float64(i+1), &total, &msg)
		session.NotificationChannel() <- mcp.JSONRPCNotification{
			JSONRPC:      "2.0",
			Notification: progress.Notification,
		}
		time.Sleep(time.Millisecond * 300)
	}

	return mcp.NewToolResultText(fmt.Sprintf("Download completed: %s!", url)), nil
}

Using the code below is sent

	server := server.ServerFromContext(ctx)
	for i := 0; i < 100; i++ {
		msg := fmt.Sprintf("Download progress: %d%%", i+1)
		server.SendNotificationToClient(
			ctx,
			"notifications/progress",
			map[string]any{
				"progress":      i,
				"total":         total,
				"progressToken": request.Params.Meta.ProgressToken,
				"message":       msg,
			},
		)
		time.Sleep(time.Millisecond * 300)
	}