hello world app with CI initial test-run

.github/workflows/ci.yml

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+name: CI Pipeline
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v3
+
+    - name: Set up Go
+      uses: actions/setup-go@v4
+      with:
+        go-version: 1.22
+
+    - name: Install dependencies
+      run: go mod tidy
+
+    - name: Build the application
+      run: go build -v ./...
+
+    - name: Run unit tests
+      run: go test -v ./...
+
+    - name: Set up Docker Buildx
+      uses: docker/setup-buildx-action@v2
+
+    - name: Log in to Docker Hub
+      uses: docker/login-action@v3
+      with:
+        username: ${{ secrets.DOCKER_USERNAME }}
+        password: ${{ secrets.DOCKER_PASSWORD }}
+
+    - name: Build and push Docker image
+      uses: docker/build-push-action@v5
+      with:
+        context: .
+        file: Dockerfile
+        push: true
+        tags: ${{ secrets.DOCKER_USERNAME }}/hello-world-server:latest
+
+    - name: Install Cosign (Container Signing Tool)
+      run: |
+        curl -LO https://github.com/sigstore/cosign/releases/download/v2.0.0/cosign-linux-amd64
+        chmod +x cosign-linux-amd64
+        sudo mv cosign-linux-amd64 /usr/local/bin/cosign
+
+    - name: Sign Docker image
+      run: cosign sign --key ${{ secrets.COSIGN_PRIVATE_KEY }} ${{ secrets.DOCKER_USERNAME }}/hello-world-server:latest

hello-world/Dockerfile

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+# Use the official Golang image for building the binary
+FROM golang:1.22-alpine AS builder
+
+# Set the working directory inside the container
+WORKDIR /app
+
+# Copy the Go module files and download dependencies
+COPY go.mod ./
+RUN go mod download
+
+# Copy the rest of the source code
+COPY . .
+
+# Build the Go binary
+RUN go build -o hello-world
+
+# Use a minimal base image to run the application
+FROM alpine:3.17
+
+# Set the working directory inside the container
+WORKDIR /app
+
+# Copy the built binary from the builder stage
+COPY --from=builder /app/hello-world .
+
+# Expose the port that the application will run on
+EXPOSE 8080
+
+# Run the Go application
+CMD ["./hello-world"]

hello-world/go.mod

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+module hello-world
+
+go 1.22.1
+
+require github.com/prometheus/client_golang v1.20.1
+
+require (
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/klauspost/compress v1.17.9 // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
+	github.com/prometheus/client_model v0.6.1 // indirect
+	github.com/prometheus/common v0.55.0 // indirect
+	github.com/prometheus/procfs v0.15.1 // indirect
+	golang.org/x/sys v0.22.0 // indirect
+	google.golang.org/protobuf v1.34.2 // indirect
+)

hello-world/go.sum

@@ -0,0 +1,24 @@
+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/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/klauspost/compress v1.17.9 h1:6KIumPrER1LHsvBVuDa0r5xaG0Es51mhhB9BQB2qeMA=
+github.com/klauspost/compress v1.17.9/go.mod h1:Di0epgTjJY877eYKx5yC51cX2A2Vl2ibi7bDH9ttBbw=
+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/prometheus/client_golang v1.20.1 h1:IMJXHOD6eARkQpxo8KkhgEVFlBNm+nkrFUyGlIu7Na8=
+github.com/prometheus/client_golang v1.20.1/go.mod h1:PIEt8X02hGcP8JWbeHyeZ53Y/jReSnHgO035n//V5WE=
+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 v0.55.0 h1:KEi6DK7lXW/m7Ig5i47x0vRzuBsHuvJdi5ee6Y3G1dc=
+github.com/prometheus/common v0.55.0/go.mod h1:2SECS4xJG1kd8XF9IcM1gMX6510RAEL65zxzNImwdc8=
+github.com/prometheus/procfs v0.15.1 h1:YagwOFzUgYfKKHX6Dr+sHT7km/hxC76UB0learggepc=
+github.com/prometheus/procfs v0.15.1/go.mod h1:fB45yRUv8NstnjriLhBQLuOUt+WW4BsoGhij/e3PBqk=
+golang.org/x/sys v0.22.0 h1:RI27ohtqKCnwULzJLqkv897zojh5/DwS/ENaMzUOaWI=
+golang.org/x/sys v0.22.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+google.golang.org/protobuf v1.34.2 h1:6xV6lTsCfpGD21XK49h7MhtcApnLqkfYgPcdHftf6hg=
+google.golang.org/protobuf v1.34.2/go.mod h1:qYOHts0dSfpeUzUFpOMr/WGzszTmLH+DiWniOlNbLDw=

hello-world/handlers.go

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+// this file will contain handlers needed for the server
+
+package main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+)
+
+// helloHandler returns a 200 OK with a "Hello, World!" message.
+func helloHandler(w http.ResponseWriter, r *http.Request) {
+	w.WriteHeader(http.StatusOK)
+	fmt.Fprintln(w, "Hello, World!")
+	log.Println("Serving hello world app")
+
+}

hello-world/main.go

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+// create main entry point for our application
+
+package main
+
+import (
+	"log"
+	"net/http"
+)
+
+func main() {
+	// Register the HTTP handlers
+	http.HandleFunc("/", helloHandler)
+	http.HandleFunc("/metrics", telemetryHandler)
+
+	// Start the HTTP server on port 8080
+	log.Println("Starting server on :8080")
+	if err := http.ListenAndServe(":8080", nil); err != nil {
+		log.Fatalf("Could not start server: %s\n", err.Error())
+	}
+}

hello-world/main_test.go

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+package main
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+// simple test case to test the helloHandler function
+
+func TestHelloHandler(t *testing.T) {
+	req, err := http.NewRequest("GET", "/", nil)
+	if err != nil {
+		t.Fatalf("Could not create request: %v", err)
+	}
+
+	rec := httptest.NewRecorder()
+	helloHandler(rec, req)
+
+	if status := rec.Code; status != http.StatusOK {
+		t.Errorf("Expected status code %v, got %v", http.StatusOK, status)
+	}
+
+	expected := "Hello, World!\n"
+	if strings.TrimSpace(rec.Body.String()) != strings.TrimSpace(expected) {
+		t.Errorf("Expected body to be '%v', got '%v'", expected, rec.Body.String())
+	}
+}
+
+// simple test case to test the telemetryHandler function
+
+func TestTelemetryHandler(t *testing.T) {
+	req, err := http.NewRequest("GET", "/metrics", nil)
+	if err != nil {
+		t.Fatalf("Could not create request: %v", err)
+	}
+
+	rec := httptest.NewRecorder()
+	telemetryHandler(rec, req)
+
+	if status := rec.Code; status != http.StatusOK {
+		t.Errorf("Expected status code %v, got %v", http.StatusOK, status)
+	}
+
+	// Simple check to ensure the output contains expected metrics name.
+	if !strings.Contains(rec.Body.String(), "http_requests_total") {
+		t.Errorf("Expected body to contain 'http_requests_total' metric, got '%v'", rec.Body.String())
+	}
+}

hello-world/telemetry.go

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+// This file handles telemetry and exposes metrics using the prometheus client library.
+
+package main
+
+import (
+	"log"
+	"net/http"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+// Define a simple counter metric
+var (
+	httpRequestsTotal = prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "http_requests_total",
+			Help: "Total number of HTTP requests",
+		},
+		[]string{"path"},
+	)
+)
+
+func init() {
+	// Register the metric with Prometheus's default registry.
+	prometheus.MustRegister(httpRequestsTotal)
+}
+
+// telemetryHandler exposes Prometheus metrics.
+func telemetryHandler(w http.ResponseWriter, r *http.Request) {
+	httpRequestsTotal.WithLabelValues(r.URL.Path).Inc()
+	promhttp.Handler().ServeHTTP(w, r)
+	log.Println("Serving basic metrics for our app")
+
+}