/** The key of the configuration. e.g. ___change__me___ */
    String APP_CIPHER_KEY = "app.cipher.key";

    /** The key of the configuration. e.g. sha256 */
    String APP_DIGEST_ALGORISM = "app.digest.algorism";

    /** The key of the configuration. e.g. .*password|.*key|.*token|.*secret */
    String APP_ENCRYPT_PROPERTY_PATTERN = "app.encrypt.property.pattern";

    /** The key of the configuration. e.g.  */

// the triple <key,value,effect> using the matching operator <operator>.
message Toleration {
  // Key is the taint key that the toleration applies to. Empty means match all taint keys.
  // If the key is empty, operator must be Exists; this combination means to match all values and all keys.
  // +optional
  optional string key = 1;

  // Operator represents a key's relationship to the value.

	// type of s is string
	// s == a[i]
	g(i, s)
}

var key string
var val interface{}  // element type of m is assignable to val
m := map[string]int{"mon":0, "tue":1, "wed":2, "thu":3, "fri":4, "sat":5, "sun":6}
for key, val = range m {
	h(key, val)
}
// key == last map key encountered in iteration
// val == map[key]

var ch chan Work = producer()
for w := range ch {
	doWork(w)
}

    *  - Created new GCE_SSH_KEY allowing specification of SSH keys for gce, gke, and kubemark.
    *  - AWS_SSH_KEY, previously assumed to be an absolute path can now be either relative or absolute

- Added `kubeadm alpha certs certificate-key` command to generate secure random key to use on `kubeadm init --experimental-upload-certs` ([#77848](https://github.com/kubernetes/kubernetes/pull/77848), [@yagonobre](https://github.com/yagonobre))

### **Scheduling**

*   Taint key `unreachable` is now in GA.
*   Taint key `notReady` is changed to `not-ready`, and is also now in GA.
*   These changes are automatically updated for taints. Tolerations for these taints must be updated manually. Specifically, you must:

- kube-controller-manager currently needs a writable `--cert-dir` (default is `/var/run/kubernetes`) for generating self-signed certificates, when no `--tls-cert-file` or `--tls-private-key-file` are provided.
- The `system:kube-controller-manager` ClusterRole lacks permission to `get` the `configmap` extension-apiserver-authentication. kube-controller-manager errors if run with a service account bound to the clusterrole.

- Kubeadm: during execution of the "check expiration" command, treat the etcd CA as external if there is a missing etcd CA key file (etcd/ca.key) and perform the proper validation on certificates signed by the...

`client-certificate: /var/lib/kubelet/pki/kubelet-client-current.pem` and `client-key: /var/lib/kubelet/pki/kubelet-client-current.pem`, replacing the embedded client certificate and key. ([#84118](https://github.com/kubernetes/kubernetes/pull/84118), [@neolit123](https://github.com/neolit123))
#### Network

    * --docker_only
    * --docker-tls
    * --docker-tls-ca
    * --docker-tls-cert
    * --docker-tls-key
    * --enable_load_reader
    * --event_storage_age_limit
    * --event_storage_event_limit
    * --global_housekeeping_interval
    * --google-json-key
    * --log_cadvisor_usage
    * --machine_id_file
    * --storage_driver_user
    * --storage_driver_password