package main
  
 import (
     "net/http"
     "sync"
 )
  
 func main() {
    var wg sync.WaitGroup
    var urls = []string{
        "http://www.golang.org/",
        "http://www.baidu.com/",
        "http://www.bokeyuan12111.com/",
    }
    for _, url := range urls {
        wg.Add(1)
        go func(url string) {
            defer wg.Done()
            resp, err := http.Get(url)
            if err != nil {
                return
            }
            resp.Body.Close()
        }(url)
    }
    wg.Wait()
}

package main
  
 import (
     "fmt"
     "net/http"
  
     "golang.org/x/sync/errgroup"
 )
  
func main() {
    var urls = []string{
        "http://www.golang.org/",
        "http://www.baidu.com/",
        "http://www.bokeyuan12111.com/",
    }
    g := new(errgroup.Group)
    for _, url := range urls {
        url := url
        g.Go(func() error {
            resp, err := http.Get(url)
            if err != nil {
                fmt.Println(err)
                return err
            }
            fmt.Printf("get [%s] success: [%d] \n", url, resp.StatusCode)
            return resp.Body.Close()
        })
    }
    if err := g.Wait(); err != nil {
        fmt.Println(err)
    } else {
        fmt.Println("All success!")
    }
}

type Group struct {
     cancel func()
  
     wg sync.WaitGroup
  
     errOnce sync.Once
     err     error
 }
  
func WithContext(ctx context.Context) (*Group, context.Context) {
    ctx, cancel := context.WithCancel(ctx)
    return &Group{cancel: cancel}, ctx
}
 
func (g *Group) Wait() error {
    g.wg.Wait()
    if g.cancel != nil {
        g.cancel()
    }
    return g.err
}
 
func (g *Group) Go(f func() error) {
    g.wg.Add(1)
 
    go func() {
        defer g.wg.Done()
 
        if err := f(); err != nil {
            g.errOnce.Do(func() {
                g.err = err
                if g.cancel != nil {
                    g.cancel()
                }
            })
        }
    }()
}

package main
 
import (
    "context"
    "fmt"
 
    "golang.org/x/sync/errgroup"
)
 
func main() {
 
    g, ctx := errgroup.WithContext(context.Background())
    dataChan := make(chan int, 20)
 
    // 數(shù)據(jù)生產(chǎn)端任務(wù)子 goroutine
    g.Go(func() error {
        defer close(dataChan)
        for i := 1; ; i++ {
            if i == 10 {
                return fmt.Errorf("data 10 is wrong")
            }
            dataChan <- i
            fmt.Println(fmt.Sprintf("sending %d", i))
        }
    })
 
    // 數(shù)據(jù)消費(fèi)端任務(wù)子 goroutine
    for i := 0; i < 3; i++ {
        g.Go(func() error {
            for j := 1; ; j++ {
                select {
                case <-ctx.Done():
                    return ctx.Err()
                case number := <-dataChan:
                    fmt.Println(fmt.Sprintf("receiving %d", number))
                }
            }
        })
    }
 
    // 主任務(wù) goroutine 等待 pipeline 結(jié)束數(shù)據(jù)流
    err := g.Wait()
    if err != nil {
        fmt.Println(err)
    }
    fmt.Println("main goroutine done!")
}