随机延时

---

package main

import (
	"fmt"
	"time"
	"github.com/gocolly/colly"
	"github.com/gocolly/colly/debug"
)

func main() {
	url := "https://httpbin.org/delay/2"

	// 实例化 collector
	c := colly.NewCollector(
		// 关联一个debugger到收集器
		colly.Debugger(&debug.LogDebugger{}),
		colly.Async(true),
	)

	// 当访问的链接匹配到  "*httpbin.*" 时， 限制colly启动的线程数为2
	c.Limit(&colly.LimitRule{
		DomainGlob:  "*httpbin.*",
		Parallelism: 2,
		RandomDelay: 5 * time.Second,
	})

	// 4个小城开始爬取 https://httpbin.org/delay/2
	for i := 0; i < 4; i++ {
		c.Visit(fmt.Sprintf("%s?n=%d", url, i))
	}
	// 开始爬取 https://httpbin.org/delay/2
	c.Visit(url)
	// 等待线程执行结束
	c.Wait()
}