在go语言中优雅退出goroutines

package main

import (

"fmt"
"sync"
"os"
"os/signal"
"syscall"
)

func consumer(messages <- chan int, shutdown <- chan int, wg *sync.WaitGroup) {

defer wg.Done()
for {

select {

case message, ok := <- messages:
//do something.
if ok {

fmt.Println(message)

} else {

 //no data , exit.
fmt.Println("no data, exit.")
return
}

case _ = <- shutdown:
//we `re done!
 //shutdown now , messages buffered channel data may be lost.
fmt.Println("all done!")
return
}
}
}

func main() {

//signals handle.
shutdown := make(chan int)
sigs := make(chan os.Signal, 1)
signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)
go func() {

sig := <- sigs
fmt.Println(sig)
//shutdown now , messages buffered channel data may be lost.
//close(shutdown)
/*or*/shutdown <- 0
} ()
messages := make(chan int, 16)

wg := &sync.WaitGroup{}
wg.Add(1)
go consumer(messages, shutdown, wg)
for i := 0; i < 10; i++ {

messages <- i
}
close(messages) //flush messages channel , no data loss.
fmt.Println("wait!")
wg.Wait()

}