ErrGroup-有错误返回的Goroutine控制

package main
import (
  "fmt"
  "time"
)
func main() {
  timeNow := time.Now()
  a := f1()
  b := f2()
  c := f3()
  fmt.Println("和为:", a+b+c)
  fmt.Println("耗时:", time.Since(timeNow))
}
func f1() int {
  time.Sleep(1e9)
  return 1
}
func f2() int {
  time.Sleep(1e9)
  return 2
}
func f3() int {
  time.Sleep(1e9)
  return 3
}

和为: 6
耗时: 3.00640904s

package main
import (
  "fmt"
  "golang.org/x/sync/errgroup"
  "time"
)
func main() {
  var (
    g = &errgroup.Group{}
    a int
    b int
    c int
  )
  timeNow := time.Now()
  g.Go(func() error {
    a = f1()
    return nil
  })
  g.Go(func() error {
    b = f2()
    return nil
  })
  g.Go(func() error {
    c = f3()
    return nil
  })
  g.Wait()
  fmt.Println("和为:", a+b+c)
  fmt.Println("耗时:", time.Since(timeNow))
}
func f1() int {
  time.Sleep(1e9)
  return 1
}
func f2() int {
  time.Sleep(1e9)
  return 2
}
func f3() int {
  time.Sleep(1e9)
  return 3
}

和为: 6
耗时: 1.003517107s