screenshot from a wrong page

[bhpike65]

1. start to run a headless chrome in background
   nohup /usr/bin/google-chrome --headless --disable-gpu --remote-debugging-port=9222 --no-sandbox --no-default-browser-check --no-first-run &

2. start different instances and take screenshot in the same time
   but they return a same page. it seems that the instance and the page not mapping correctly, and instance cannot be Shutdown() how it closes the page?

./screenshot https://www.google.com google.png
./screenshot https://www.bing.com bing.png

package main

import (
        "context"
        "io/ioutil"
        "log"
        "time"
        "os"
        "github.com/chromedp/cdproto/cdp"
        "github.com/chromedp/cdproto/page"
        "github.com/chromedp/chromedp"
        "github.com/chromedp/cdproto/emulation"
)

func main() {
        if len(os.Args) != 3 {
                panic("argc")
        }
        site := os.Args[1]
        filename := os.Args[2]

        var err error

        // create context
        ctxt, cancel := context.WithCancel(context.Background())
        defer cancel()

        // create chrome instance
        c, err := chromedp.New(ctxt, chromedp.WithLog(log.Printf))
        if err != nil {
                log.Fatal(err)
        }

        metrics := emulation.SetDeviceMetricsOverride(1920, 1080, 0, false)
        if err = c.Run(ctxt, metrics); err != nil {
                log.Println(err)
                return
        }

        // run task list
        var buf []byte

        if err = c.Run(ctxt, screenshotTask(site, &buf)); err != nil {
                log.Println(err)
                return
        }
/*
        if err = c.Shutdown(ctxt); err != nil {
                log.Println(err)
        }
*/
        // write to disk
        err = ioutil.WriteFile(filename, buf, 0644)
        if err != nil {
                log.Println(err)
                return
        }
}

func screenshotTask(url string, picbuf *[]byte) chromedp.Action {
        return chromedp.Tasks{
                /*
                chromedp.ActionFunc(func(ctx context.Context, h cdp.Executor) error {
                        _, err := network.SetCookie("customKey", "meaningless").WithURL(url).Do(ctx, h)
                        return err
                }),
                */
                chromedp.Navigate(url),
                chromedp.Sleep(5000 * time.Millisecond),
                chromedp.ActionFunc(func(ctxt context.Context, h cdp.Executor) error {
                        buf, err := page.CaptureScreenshot().Do(ctxt, h)
                        if err != nil {
                                return err
                        }
                        *picbuf = buf
                        return nil
                }),
        }
}