将判空与读取放在一个事务中

func producer(c chan<- int) {
    var i int = 1
    for {
        time.Sleep(2 * time.Second)
        ok := trySend(c, i)
        if ok {
            fmt.Printf("[producer]: send [%d] to channel\n", i)
            i++
            continue
        }
        fmt.Printf("[producer]: try send [%d], but channel is full\n", i)
    }
}

func tryRecv(c <-chan int) (int, bool) {
    select {
    case i := <-c:
        return i, true

    default:
        return 0, false
    }
}

func trySend(c chan<- int, i int) bool {
    select {
    case c <- i:
        return true
    default:
        return false
    }
}

func consumer(c <-chan int) {
    for {
        i, ok := tryRecv(c)
        if !ok {
            fmt.Println("[consumer]: try to recv from channel, but the channel is empty")
            time.Sleep(1 * time.Second)
            continue
        }
        fmt.Printf("[consumer]: recv [%d] from channel\n", i)
        if i >= 3 {
            fmt.Println("[consumer]: exit")
            return
        }
    }
}

func main() {
    var wg sync.WaitGroup
    c := make(chan int, 3)
    wg.Add(2)
    go func() {
        producer(c)
        wg.Done()
    }()

    go func() {
        consumer(c)
        wg.Done()
    }()

    wg.Wait()
}