https://gist.github.com/kachayev/3124594#file-go-channels-7-search-go

go-channels-7-search.go

// Channels-driven concurrency with Go
// Code examples from Rob Pike's talk on Google I/O 2012:
// http://www.youtube.com/watch?v=f6kdp27TYZs&feature=youtu.be
//
// Concurrency is the key to designing high performance network services. 
// Go's concurrency primitives (goroutines and channels) provide a simple and efficient means 
// of expressing concurrent execution. In this talk we see how tricky concurrency 
// problems can be solved gracefully with simple Go code.

// (7) Fake Google search

var (
    Web = fakeSearch("web")
    Image = fakeSearch("image")
    Video = fakeSearch("video")
)

type Search func(query string) Result

func fakeSearch(kind string) Search {
    return func(query string) Result {
        time.Sleep(time.Duration(rand.Intn(100)) * time.Millisecond)
        return Result(fmt.Sprintf("%s result for %q\n", kind, query))
    }
}

// Replication in order to avoid timeouts
func First(query string, replicas ...Search) Result {
    c := make(chan Result)
    searchReplica := func(i, int) { c <- replicas[i](query) }
    for i := range replicas {
        go searchReplica(i)
    }
    return <-c
}

// Main search function
func Google(query sting) (results []Result) {
    c := make(chan Result)

    go func() { c <- First(query, Web1, Web2) }()
    go func() { c <- First(query, Image1, Image2) }()
    go func() { c <- First(query, Video1, Video2) }()

    timeout := time.After(80 * time.Millisecond)

    for i := 0; i < 3; i++ {
        select {
            case result := <-c:
                results = append(results, result)
            case <-timeout:
                fmt.Println("timed out.")
                return
        }
    }
}