README.md: update Usage case

fuweid · fuweid · commit 8ffba88879e7 · 2020-06-14T10:53:38.000+08:00
Signed-off-by: Wei Fu &lt;fuweid89@gmail.com&gt;
diff --git a/README.md b/README.md
@@ -13,35 +13,67 @@ go-cni aims to support plugins that implement [Container Network Interface](http
 
 ## Usage
 ```go
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	gocni "github.com/containerd/go-cni"
+)
+
 func main() {
-	id := "123456"
-	netns := "/proc/9999/ns/net"
+	id := "example"
+	netns := "/var/run/netns/example-ns-1"
+
+	// CNI allows multiple CNI configurations and the network interface
+	// will be named by eth0, eth1, ..., ethN.
+	ifPrefixName := "eth"
 	defaultIfName := "eth0"
-	// Initialize library
-	l = gocni.New(gocni.WithMinNetworkCount(2),
-		gocni.WithPluginConfDir("/etc/mycni/net.d"),
-		gocni.WithPluginDir([]string{"/opt/mycni/bin", "/opt/cni/bin"}),
-		gocni.WithDefaultIfName(defaultIfName))
-	
+
+	// Initializes library
+	l, err := gocni.New(
+		// one for loopback network interface
+		gocni.WithMinNetworkCount(2),
+		gocni.WithPluginConfDir("/etc/cni/net.d"),
+		gocni.WithPluginDir([]string{"/opt/cni/bin"}),
+		// Sets the prefix for network interfaces, eth by default
+		gocni.WithInterfacePrefix(ifPrefixName))
+	if err != nil {
+		log.Fatalf("failed to initialize cni library: %v", err)
+	}
+
 	// Load the cni configuration
-	err:= l.Load(gocni.WithLoNetwork, gocni.WithDefaultConf)
-        if err != nil{
-		log.Errorf("failed to load cni configuration: %v", err)
-		return 
+	if err := l.Load(gocni.WithLoNetwork, gocni.WithDefaultConf); err != nil {
+		log.Fatalf("failed to load cni configuration: %v", err)
 	}
-	
+
 	// Setup network for namespace.
 	labels := map[string]string{
 		"K8S_POD_NAMESPACE":          "namespace1",
 		"K8S_POD_NAME":               "pod1",
 		"K8S_POD_INFRA_CONTAINER_ID": id,
+		// Plugin tolerates all Args embedded by unknown labels, like
+		// K8S_POD_NAMESPACE/NAME/INFRA_CONTAINER_ID...
+		"IgnoreUnknown": "1",
 	}
-	result, err := l.Setup(id, netns, gocni.WithLabels(labels))
+
+	ctx := context.Background()
+
+	// Teardown network
+	defer func() {
+		if err := l.Remove(ctx, id, netns, gocni.WithLabels(labels)); err != nil {
+			log.Fatalf("failed to teardown network: %v", err)
+		}
+	}()
+
+	// Setup network
+	result, err := l.Setup(ctx, id, netns, gocni.WithLabels(labels))
 	if err != nil {
-		log.Errorf("failed to setup network for namespace %q: %v",id, err)
-		return 
+		log.Fatalf("failed to setup network for namespace: %v", err)
 	}
-	
+
 	// Get IP of the default interface
 	IP := result.Interfaces[defaultIfName].IPConfigs[0].IP.String()
 	fmt.Printf("IP of the default interface %s:%s", defaultIfName, IP)
