Golang Go语言中《GO 语言圣经》里这句话应该怎么解释？

下面这段代码来自《 GO 语言圣经》 8.6. 示例: 并发的 Web 爬虫

func main() {
    worklist := make(chan []string)  // lists of URLs, may have duplicates
    unseenLinks := make(chan string) // de-duplicated URLs

    // Add command-line arguments to worklist.
    go func() { worklist <- os.Args[1:] }()

    // Create 20 crawler goroutines to fetch each unseen link.
    for i := 0; i < 20; i++ {
        go func() {
            for link := range unseenLinks {
                foundLinks := crawl(link)
                go func() { worklist <- foundLinks }() //避免死锁
            }
        }()
    }

    // The main goroutine de-duplicates worklist items
    // and sends the unseen ones to the crawlers.
    seen := make(map[string]bool)
    for list := range worklist {
        for _, link := range list {
            if !seen[link] {
                seen[link] = true
                unseenLinks <- link
            }
        }
    }
}

书里面说，“crawl 函数爬到的链接在一个专有的 goroutine 中被发送到 worklist 中来避免死锁”，就是上面代码中加了中文注释那一行，为什么不把 worklist <- foundLinks 这个操作加入专有协程就有引起死锁呢？