update client-go to the latest version in order to keep in sync with …

…client-go example

content/en/docs/tasks/administer-cluster/access-cluster-api.md

@@ -161,28 +161,38 @@ Kubernetes officially supports client libraries for [Go](#go-client) and
 
 #### Go client
 
-* To get the library, run the following command: `go get k8s.io/client-go/<version number>/kubernetes` See [https://github.com/kubernetes/client-go](https://github.com/kubernetes/client-go) to see which versions are supported.
-* Write an application atop of the client-go clients. Note that client-go defines its own API objects, so if needed, please import API definitions from client-go rather than from the main repository, e.g., `import "k8s.io/client-go/1.4/pkg/api/v1"` is correct.
+* To get the library, run the following command: `go get k8s.io/client-go@kubernetes-<Kubernetes version number>` See [https://github.com/kubernetes/client-go](https://github.com/kubernetes/client-go) to see which versions are supported.
+* Write an application atop of the client-go clients. Note that client-go defines its own API objects, so if needed, import API definitions from client-go rather than from the main repository. For example, `import "k8s.io/client-go/kubernetes"` is correct.
+
+{{< note >}}
+
+According to the [README](https://github.com/kubernetes/client-go/blob/master/README.md), the client-go responsitory is still a mirror of [https://github.com/kubernetes/kubernetes/tree/master/staging/src/k8s.io/client-go](https://github.com/kubernetes/kubernetes/tree/master/staging/src/k8s.io/client-go), the code development is in the staging area. Since Kubernetes 1.8 release, the client-go library syncs the Kubernetes version tags to client-go when syncing the code from the staging area, prefixed with "kubernetes-". For example, if you check out the kubernetes-1.15.3 tag in client-go, the code you get is exactly the same as you check out the v1.15.3 tag in Kubernetes, and change directory to `staging/src/k8s.io/client-go`. 
+
+The `<Kubernetes version number>` can also be `HEAD`, and the `HEAD` follows the upstream Kubernetes repo.
+
+{{< /note >}}
 
 The Go client can use the same [kubeconfig file](/docs/concepts/cluster-administration/authenticate-across-clusters-kubeconfig/)
 as the kubectl CLI does to locate and authenticate to the API server. See this [example](https://git.k8s.io/client-go/examples/out-of-cluster-client-configuration/main.go):
 
 ```golang
 import (
-   "fmt"
-   "k8s.io/client-go/1.4/kubernetes"
-   "k8s.io/client-go/1.4/pkg/api/v1"
-   "k8s.io/client-go/1.4/tools/clientcmd"
+  "fmt"
+  "k8s.io/apimachinery/pkg/apis/meta/v1"
+  "k8s.io/client-go/kubernetes"
+  "k8s.io/client-go/tools/clientcmd"
 )
-...
-   // uses the current context in kubeconfig
-   config, _ := clientcmd.BuildConfigFromFlags("", "path to kubeconfig")
-   // creates the clientset
-   clientset, _:= kubernetes.NewForConfig(config)
-   // access the API to list pods
-   pods, _:= clientset.CoreV1().Pods("").List(v1.ListOptions{})
-   fmt.Printf("There are %d pods in the cluster\n", len(pods.Items))
-...
+
+func main() {
+  // uses the current context in kubeconfig
+  // path to kubeconfig -- e.g., /root/.kube/config
+  config, _ := clientcmd.BuildConfigFromFlags("", "<path to kubeconfig>")
+  // creates the clientset
+  clientset, _ := kubernetes.NewForConfig(config)
+  // access the API to list pods
+  pods, _ := clientset.CoreV1().Pods("").List(v1.ListOptions{})
+  fmt.Printf("There are %d pods in the cluster\n", len(pods.Items))
+}
 ```
 
 If the application is deployed as a Pod in the cluster, please refer to the [next section](#accessing-the-api-from-a-pod).