Go Playground exercise

CHSHJ

package main　　

　　
import (
　　
     "fmt"
　　
     "sync"
　　
)
　　

　　
type Fetcher interface {
　　
     // Fetch returns the body of URL and
　　
     // a slice of URLs found on that page.
　　
     Fetch(url string) (body string, urls []string, err error)
　　
}
　　

　　
// Crawl uses fetcher to recursively crawl
　　
// pages starting with url, to a maximum of depth.
　　
func Crawl(url string, depth int, fetcher Fetcher, c *urlSync, wg *sync.WaitGroup) {
　　
     // TODO: Fetch URLs in parallel.
　　
     // TODO: Don't fetch the same URL twice.
　　
     // This implementation doesn't do either:
　　
     defer wg.Done()
　　
     if depth