Golang Web Crawler Solution

package main

import (
	"fmt"
)

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)
}

type unprocessed struct {
	depth int
	url[] string
}

func getPage(url string, depth int, r chan unprocessed){
	body, urls, err := fetcher.Fetch(url)
	fmt.Printf("found: %s %q\n", url, body)
	
	if err != nil {
		fmt.Println(err)
	}
	
	r <- unprocessed{ depth - 1, urls }
}

func Crawl(url string, depth int, fetcher Fetcher) {
	
	//setup channel for inputs to be processed
	up := make(chan unprocessed, 0)
	
	//kick off processing and count how many pages are left to process
	go getPage(url, depth, up)
	outstanding := 1
	
	visited := make(map[string]bool)
	for outstanding > 0 {
		
		//pop a visit from the channel
		next := <-up
		outstanding--
		
		//if were too deep, skip it
		if next.depth <= 0 {
			continue
		}
		
		//loop over all urls to visit from that page
		for _, link := range next.url {
			
			//check we havent visited them before
			if visited[link] {
				continue
			}
			
			//all good to visit them
			outstanding++
			visited[link] = true
			go getPage(link, depth, up)
		}
	}
}

func main() {
	Crawl("http://golang.org/", 4, fetcher)
}

// fakeFetcher is Fetcher that returns canned results.
type fakeFetcher map[string]*fakeResult

type fakeResult struct {
	body string
	urls []string
}

func (f fakeFetcher) Fetch(url string) (string, []string, error) {
	if res, ok := f[url]; ok {
		return res.body, res.urls, nil
	}
	return "", nil, fmt.Errorf("not found: %s", url)
}

// fetcher is a populated fakeFetcher.
var fetcher = fakeFetcher{
	"http://golang.org/": &fakeResult{
		"The Go Programming Language",
		[]string{
			"http://golang.org/pkg/",
			"http://golang.org/cmd/",
		},
	},
	"http://golang.org/pkg/": &fakeResult{
		"Packages",
		[]string{
			"http://golang.org/",
			"http://golang.org/cmd/",
			"http://golang.org/pkg/fmt/",
			"http://golang.org/pkg/os/",
		},
	},
	"http://golang.org/pkg/fmt/": &fakeResult{
		"Package fmt",
		[]string{
			"http://golang.org/",
			"http://golang.org/pkg/",
		},
	},
	"http://golang.org/pkg/os/": &fakeResult{
		"Package os",
		[]string{
			"http://golang.org/",
			"http://golang.org/pkg/",
		},
	},
}