Go 并发控制 errgroup.Group的实现示例

package main
import (
 "fmt"
 "time"
 "golang.org/x/sync/errgroup"
)
func main() {
 g := &errgroup.Group{}
 for i := 0; i < 5; i++ {
  index := i
  g.Go(func() error {
   fmt.Printf("start to execute the %d gorouting\n", index)
   time.Sleep(time.Duration(index) * time.Second)
   if index%2 == 0 {
    return fmt.Errorf("something has failed on grouting:%d", index)
   }
   fmt.Printf("gorouting:%d end\n", index)
   return nil
  })
 }
 if err := g.Wait(); err != nil {
  fmt.Println(err)
 }
}
// Output:
// start to execute the 4 gorouting
// start to execute the 1 gorouting
// start to execute the 0 gorouting
// start to execute the 2 gorouting
// start to execute the 3 gorouting
// gorouting:1 end
// gorouting:3 end
// something has failed on grouting:0

g, _ := errgroup.WithContext(context.Background()) // 支持 context

 ...
 if err := g.Wait(); err != nil {
  fmt.Println(err)
 }
 if err := g.Wait(); err != nil { // 可再次调用 Wait，依然可以得到 group 的 error 信息
  fmt.Println(err)
 }

package main
import (
 "log"
 "time"
 "golang.org/x/sync/errgroup"
)
func main() {
 jobs := make(chan int, 10)
 go func() {
  for i := 0; i < 8; i++ {
   jobs <- i + 1
  }
  close(jobs)
 }()
 eg:= &errgroup.Group{}
 eg.SetLimit(3)
 for j := range jobs {
  j := j
  eg.Go(func() error {
   log.Printf("handle job: %d\n", j)
   time.Sleep(2 * time.Second)
   return nil
  })
 }
 eg.Wait()
}