```
func main() {
for i := 0; i < 4; i++ {
queryAll()
fmt.Printf("goroutines: %d\n", runtime.NumGoroutine())
}
}
func queryAll() int {
ch := make(chan int)
for i := 0; i < 3; i++ {
go func() { ch <- query() }()
}
return <-ch
}
func query() int {
n := rand.Intn(100)
time.Sleep(time.Duration(n) * time.Millisecond)
return n
}
```
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