fix concurrent issue in buffer handling of package grand

.example/other/test2.go

@@ -2,47 +2,11 @@ package main
 
 import (
 	"fmt"
-	"net"
 )
 
-func getMacAddrs() (macAddrs []string) {
-	netInterfaces, err := net.Interfaces()
-	if err != nil {
-		fmt.Printf("fail to get net interfaces: %v", err)
-		return macAddrs
-	}
-
-	for _, netInterface := range netInterfaces {
-		macAddr := netInterface.HardwareAddr.String()
-		if len(macAddr) == 0 {
-			continue
-		}
-
-		macAddrs = append(macAddrs, macAddr)
-	}
-	return macAddrs
-}
-
-func getIPs() (ips []string) {
-
-	interfaceAddr, err := net.InterfaceAddrs()
-	if err != nil {
-		fmt.Printf("fail to get net interface addrs: %v", err)
-		return ips
-	}
-
-	for _, address := range interfaceAddr {
-		ipNet, isValidIpNet := address.(*net.IPNet)
-		if isValidIpNet && !ipNet.IP.IsLoopback() {
-			if ipNet.IP.To4() != nil {
-				ips = append(ips, ipNet.IP.String())
-			}
-		}
-	}
-	return ips
-}
-
 func main() {
-	fmt.Printf("mac addrs: %q\n", getMacAddrs())
-	fmt.Printf("ips: %q\n", getIPs())
+	b1 := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 0}
+	b2 := b1[:2]
+	b1[0] = 9
+	fmt.Println(b2)
 }