add readme for kubernetes.

Signed-off-by: Bo-Yi Wu <[email protected]>

Author: appleboy

example19-deploy-with-kubernetes/README.md

@@ -0,0 +1,154 @@
+# Deploy golang app using drone with Kubernetes
+
+See the [chinese blog](https://blog.wu-boy.com/2018/06/drone-kubernetes-with-golang/)
+
+## write simple golang app
+
+see the [main.go](./main.go)
+
+```go
+package main
+
+import (
+	"log"
+	"net/http"
+	"os"
+	"strings"
+)
+
+var version = "master"
+
+func showVersion(w http.ResponseWriter, r *http.Request) {
+	log.Println(version)
+	w.Write([]byte(version))
+}
+
+func sayHello(w http.ResponseWriter, r *http.Request) {
+	message := r.URL.Path
+	message = strings.TrimPrefix(message, "/")
+	message = "Hello, got the message: " + message
+	log.Println(message)
+	w.Write([]byte(message))
+}
+
+func main() {
+	// use PORT environment variable, or default to 8080
+	port := "8080"
+	if fromEnv := os.Getenv("PORT"); fromEnv != "" {
+		port = fromEnv
+	}
+	http.HandleFunc("/version", showVersion)
+	http.HandleFunc("/", sayHello)
+	log.Println("Listen server on " + port + " port")
+	if err := http.ListenAndServe(":"+port, nil); err != nil {
+		log.Fatal(err)
+	}
+}
+```
+
+write app version using `-ldflags`. see the following example:
+
+```makefile
+build:
+ifneq ($(DRONE_TAG),)
+    go build -v -ldflags "-X main.version=$(DRONE_TAG)" -a -o release/linux/amd64/hello
+else
+    go build -v -ldflags "-X main.version=$(DRONE_COMMIT)" -a -o release/linux/amd64/hello
+endif
+```
+
+how to build binary using drone?
+
+```yaml
+pipeline:
+  build_linux_amd64:
+    image: golang:1.10
+    group: build
+    environment:
+      - GOOS=linux
+      - GOARCH=amd64
+      - CGO_ENABLED=0
+    commands:
+      - cd example19-deploy-with-kubernetes && make build
+```
+
+## upload to dockerhub
+
+See the drone config:
+
+```yaml
+docker_golang:
+  image: plugins/docker:17.12
+  secrets: [ docker_username, docker_password ]
+  repo: appleboy/golang-http
+  dockerfile: example19-deploy-with-kubernetes/Dockerfile
+  default_tags: true
+  when:
+    event: [ push, tag ]
+```
+
+## rolling update using kubernetes
+
+Please preare the following drone secrets
+
+1. KUBERNETES_SERVER
+2. KUBERNETES_CERT
+3. KUBERNETES_TOKEN
+
+then see the drone config
+
+```yaml
+deploy:
+  image: sh4d1/drone-kubernetes
+  kubernetes_template: example19-deploy-with-kubernetes/deployment.yml
+  kubernetes_namespace: default
+  secrets: [ kubernetes_server, kubernetes_cert, kubernetes_token ]
+```
+
+see the `deployment.yaml`
+
+```yaml
+apiVersion: extensions/v1beta1
+kind: Deployment
+metadata:
+  name: frontend
+  # these labels can be applied automatically
+  # from the labels in the pod template if not set
+  labels:
+    app: gotraining
+    tier: frontend
+spec:
+  # this replicas value is default
+  # modify it according to your case
+  replicas: 3
+  # selector can be applied automatically
+  # from the labels in the pod template if not set
+  # selector:
+  #   app: guestbook
+  #   tier: frontend
+  strategy:
+    type: RollingUpdate
+    rollingUpdate:
+      maxSurge: 1
+      maxUnavailable: 1
+  minReadySeconds: 5
+  template:
+    metadata:
+      labels:
+        app: gotraining
+        tier: frontend
+    spec:
+      containers:
+      - name: go-hello
+        image: appleboy/golang-http:VERSION
+        imagePullPolicy: Always
+        resources:
+          requests:
+            cpu: 100m
+            memory: 100Mi
+        ports:
+        - containerPort: 8080
+        env:
+        - name: FOR_GODS_SAKE_PLEASE_REDEPLOY
+          value: 'THIS_STRING_IS_REPLACED_DURING_BUILD'
+```