Initial scaffold: Go service, Helm chart, Kustomize overlays

.gitignore

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+hello-svc

Dockerfile

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+FROM golang:1.23-alpine AS builder
+WORKDIR /app
+COPY go.mod go.sum ./
+RUN go mod download
+COPY . .
+RUN CGO_ENABLED=0 GOOS=linux go build -ldflags="-s -w" -o hello-svc .
+
+FROM gcr.io/distroless/static-debian12
+COPY --from=builder /app/hello-svc /hello-svc
+EXPOSE 8080
+ENTRYPOINT ["/hello-svc"]

go.mod

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+module git.samidare.dev/rod/hello-svc
+
+go 1.23
+
+require github.com/prometheus/client_golang v1.22.0
+
+require (
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
+	github.com/prometheus/client_model v0.6.1 // indirect
+	github.com/prometheus/common v0.62.0 // indirect
+	github.com/prometheus/procfs v0.15.1 // indirect
+	golang.org/x/sys v0.30.0 // indirect
+	google.golang.org/protobuf v1.36.5 // indirect
+)

go.sum

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+github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
+github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
+github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
+github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
+github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
+github.com/klauspost/compress v1.18.0 h1:c/Cqfb0r+Yi+JtIEq73FWXVkRonBlf0CRNYc8Zttxdo=
+github.com/klauspost/compress v1.18.0/go.mod h1:2Pp+KzxcywXVXMr50+X0Q/Lsb43OQHYWRCY2AiWywWQ=
+github.com/kylelemons/godebug v1.1.0 h1:RPNrshWIDI6G2gRW9EHilWtl7Z6Sb1BR0xunSBf0SNc=
+github.com/kylelemons/godebug v1.1.0/go.mod h1:9/0rRGxNHcop5bhtWyNeEfOS8JIWk580+fNqagV/RAw=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 h1:C3w9PqII01/Oq1c1nUAm88MOHcQC9l5mIlSMApZMrHA=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822/go.mod h1:+n7T8mK8HuQTcFwEeznm/DIxMOiR9yIdICNftLE1DvQ=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/prometheus/client_golang v1.22.0 h1:rb93p9lokFEsctTys46VnV1kLCDpVZ0a/Y92Vm0Zc6Q=
+github.com/prometheus/client_golang v1.22.0/go.mod h1:R7ljNsLXhuQXYZYtw6GAE9AZg8Y7vEW5scdCXrWRXC0=
+github.com/prometheus/client_model v0.6.1 h1:ZKSh/rekM+n3CeS952MLRAdFwIKqeY8b62p8ais2e9E=
+github.com/prometheus/client_model v0.6.1/go.mod h1:OrxVMOVHjw3lKMa8+x6HeMGkHMQyHDk9E3jmP2AmGiY=
+github.com/prometheus/common v0.62.0 h1:xasJaQlnWAeyHdUBeGjXmutelfJHWMRr+Fg4QszZ2Io=
+github.com/prometheus/common v0.62.0/go.mod h1:vyBcEuLSvWos9B1+CyL7JZ2up+uFzXhkqml0W5zIY1I=
+github.com/prometheus/procfs v0.15.1 h1:YagwOFzUgYfKKHX6Dr+sHT7km/hxC76UB0learggepc=
+github.com/prometheus/procfs v0.15.1/go.mod h1:fB45yRUv8NstnjriLhBQLuOUt+WW4BsoGhij/e3PBqk=
+github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
+github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
+golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+google.golang.org/protobuf v1.36.5 h1:tPhr+woSbjfYvY6/GPufUoYizxw1cF/yFoxJ2fmpwlM=
+google.golang.org/protobuf v1.36.5/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

k8s/base/kustomization.yaml

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+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+helmCharts:
+  - name: hello-svc
+    releaseName: hello-svc
+    localChartPath: ../../helm/hello-svc
+    valuesFile: values.yaml

k8s/base/values.yaml

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+# Base Helm values — overlays patch on top of this via strategic merge.
+replicaCount: 1
+
+image:
+  repository: git.samidare.dev/rod/hello-svc
+  pullPolicy: Always
+  tag: "latest"
+
+env:
+  APP_ENV: production
+  LOG_LEVEL: info
+  APP_VERSION: unknown
+
+resources:
+  requests:
+    cpu: 100m
+    memory: 64Mi
+  limits:
+    cpu: 500m
+    memory: 128Mi
+
+serviceMonitor:
+  enabled: true
+  interval: 30s

k8s/overlays/dev/deployment-patch.yaml

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+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: hello-svc
+spec:
+  replicas: 1
+  template:
+    spec:
+      containers:
+        - name: hello-svc
+          env:
+            - name: APP_ENV
+              value: dev
+            - name: LOG_LEVEL
+              value: debug
+          resources:
+            requests:
+              cpu: 50m
+              memory: 32Mi
+            limits:
+              cpu: 100m
+              memory: 64Mi

k8s/overlays/dev/kustomization.yaml

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+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+namespace: dev
+
+resources:
+  - ../../base
+  - namespace.yaml
+
+patches:
+  - path: deployment-patch.yaml

k8s/overlays/dev/namespace.yaml

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+apiVersion: v1
+kind: Namespace
+metadata:
+  name: dev

k8s/overlays/prod/deployment-patch.yaml

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+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: hello-svc
+spec:
+  replicas: 3
+  template:
+    spec:
+      containers:
+        - name: hello-svc
+          env:
+            - name: APP_ENV
+              value: prod
+            - name: LOG_LEVEL
+              value: info
+          resources:
+            requests:
+              cpu: 100m
+              memory: 64Mi
+            limits:
+              cpu: 500m
+              memory: 128Mi

k8s/overlays/prod/kustomization.yaml

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+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+namespace: prod
+
+resources:
+  - ../../base
+  - namespace.yaml
+
+patches:
+  - path: deployment-patch.yaml

k8s/overlays/prod/namespace.yaml

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+apiVersion: v1
+kind: Namespace
+metadata:
+  name: prod

main.go

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+package main
+
+import (
+	"encoding/json"
+	"log/slog"
+	"net/http"
+	"os"
+	"strconv"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+var (
+	reqTotal = promauto.NewCounterVec(prometheus.CounterOpts{
+		Name: "http_requests_total",
+		Help: "Total number of HTTP requests.",
+	}, []string{"method", "path", "status"})
+
+	reqDuration = promauto.NewHistogramVec(prometheus.HistogramOpts{
+		Name:    "http_request_duration_seconds",
+		Help:    "HTTP request latency in seconds.",
+		Buckets: prometheus.DefBuckets,
+	}, []string{"method", "path"})
+)
+
+func main() {
+	env := getenv("APP_ENV", "dev")
+	version := getenv("APP_VERSION", "unknown")
+	port := getenv("PORT", "8080")
+
+	logLevel := slog.LevelInfo
+	if getenv("LOG_LEVEL", "info") == "debug" {
+		logLevel = slog.LevelDebug
+	}
+	slog.SetDefault(slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{Level: logLevel})))
+
+	mux := http.NewServeMux()
+	mux.Handle("/metrics", promhttp.Handler())
+	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	})
+	mux.HandleFunc("/", instrument(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(map[string]string{
+			"env":     env,
+			"version": version,
+		})
+	}))
+
+	slog.Info("listening", "port", port, "env", env, "version", version)
+	if err := http.ListenAndServe(":"+port, mux); err != nil {
+		slog.Error("server failed", "err", err)
+		os.Exit(1)
+	}
+}
+
+func instrument(next http.HandlerFunc) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		rw := &statusWriter{ResponseWriter: w, status: http.StatusOK}
+		start := time.Now()
+		next(rw, r)
+		dur := time.Since(start).Seconds()
+		status := strconv.Itoa(rw.status)
+		reqTotal.WithLabelValues(r.Method, r.URL.Path, status).Inc()
+		reqDuration.WithLabelValues(r.Method, r.URL.Path).Observe(dur)
+		slog.Debug("request", "method", r.Method, "path", r.URL.Path, "status", rw.status, "duration", dur)
+	}
+}
+
+type statusWriter struct {
+	http.ResponseWriter
+	status int
+}
+
+func (sw *statusWriter) WriteHeader(code int) {
+	sw.status = code
+	sw.ResponseWriter.WriteHeader(code)
+}
+
+func getenv(key, fallback string) string {
+	if v := os.Getenv(key); v != "" {
+		return v
+	}
+	return fallback
+}