实例说明golang并发

package main
import (
 "fmt"
 "math/rand"
 "time"
)
func main() {
 rand.Seed(time.Now().UnixNano())
 start := time.Now()
 results := Google("golang")
 fmt.Println(results)
 fmt.Printf("%s", time.Since(start))
}
type Result string
type Search func(key string) Result
func ResourceSearch(kind string) Search {
 return func(key string) Result {
 time.Sleep(time.Duration(rand.Intn(100)) * time.Millisecond)
 return Result(fmt.Sprintf("<%s from %s server>\n", key, kind))
 }
}
func FirstSearch(servers []Search, key string) Result {
 result := make(chan Result)
 done := make(chan struct{})
 defer close(done)
 first := func(i int) {
 select {
 case <-done:
 return
 case result <- servers[i](key):
 }
 }
 for i := range servers {
 go first(i)
 }
 return <-result
}
func Google(key string) (results []Result) {
 var images []Search
 var videos []Search
 var voices []Search
 for i := 0; i < 3; i++ {
 images = append(images, ResourceSearch(fmt.Sprintf("image-%d", i)))
 videos = append(videos, ResourceSearch(fmt.Sprintf("video-%d", i)))
 voices = append(voices, ResourceSearch(fmt.Sprintf("voice-%d", i)))
 }
 chanResults := make(chan Result)
 go func() {
 chanResults <- FirstSearch(images, key)
 }()
 go func() {
 chanResults <- FirstSearch(videos, key)
 }()
 go func() {
 chanResults <- FirstSearch(voices, key)
 }()
 after := time.After(80 * time.Millisecond)
 for i := 0; i < 3; i++ {
 select {
 case r := <-chanResults:
 results = append(results, r)
 case <-after:
 fmt.Println("timeout")
 return
 }
 }
 return
}

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