Creating Makefile. Adding .idea files. Updating main.go : Configuration of the application and the server. Creating our first handler for the endpoint /v1/healthcheck with healtcheck.go file.

.idea/.gitignore

@@ -0,0 +1,10 @@
+# Default ignored files
+/shelf/
+/workspace.xml
+# Editor-based HTTP Client requests
+/httpRequests/
+# Environment-dependent path to Maven home directory
+/mavenHomeManager.xml
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml

.idea/greenlight.iml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="Go" enabled="true" />
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$" />
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>

.idea/misc.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_23" default="true" project-jdk-name="openjdk-23" project-jdk-type="JavaSDK">
+    <output url="file://$PROJECT_DIR$/out" />
+  </component>
+</project>

.idea/modules.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectModuleManager">
+    <modules>
+      <module fileurl="file://$PROJECT_DIR$/.idea/greenlight.iml" filepath="$PROJECT_DIR$/.idea/greenlight.iml" />
+    </modules>
+  </component>
+</project>

.idea/vcs.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="" vcs="Git" />
+  </component>
+</project>

cmd/api/healthcheck.go

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+package main
+
+import (
+	"fmt"
+	"net/http"
+)
+
+/*
+Declare a handler which writes a plain-text response with information about the
+application status, operating environment and version
+*/
+/*
+Tips: The important thing to point out here is that healthcheckHandler is implemented as a method
+on our application struct. This is an effective and idiomatic way to make dependencies available
+to our handlers without resorting to global variables or closures - any dependency that the
+healthcheckHandler needs can simply be included as a field in the application struct when we
+initialize it in main()
+*/
+func (app *application) healthcheckHandler(w http.ResponseWriter, r *http.Request) {
+	fmt.Fprintln(w, "status: available")
+	fmt.Fprintf(w, "environment: %s\n", app.config.env)
+	fmt.Fprintf(w, "version: %s\n", version)
+}

cmd/api/main.go

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+package main
+
+import (
+	"flag"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"os"
+	"time"
+)
+
+/*
+Declare a string containing the application version number.
+Later we'll generate this automatically at build time, but for now we'll just store the
+version number as a hard-coded global constant.
+*/
+const version = "1.0.0"
+
+/*
+Define a config struct to hold all the configuration settings  for our application.
+For now, the only configuration settings will be the network port that we want the server to listen on,
+and the name of the current operating environment for the application (development, staging, production, etc.)
+We'll read in the configuration settings from command-line flags when the application starts.
+*/
+type config struct {
+	port int
+	env  string
+}
+
+/*
+Define an application struct to hold the dependencies for our HTTP handlers, helpers,
+and middleware.
+*/
+type application struct {
+	config config
+	logger *slog.Logger
+}
+
+func main() {
+	// Declare an instance of the config struct.
+	var cfg config
+
+	/*
+		Read the value of the port and env command-line flags into the config struct.
+		We default to using the port number 4000 and the environment "development" if no corresponding flags are provided.
+	*/
+	flag.IntVar(&cfg.port, "port", 4000, "API server port")
+	flag.StringVar(&cfg.env, "env", "development", "Environment (development|staging|production")
+	flag.Parse()
+
+	// Initialize a new structured logger which writes log entries to standard out stream.
+	logger := slog.New(slog.NewTextHandler(os.Stdout, nil))
+
+	// Declare an instance of the application struct, containing the config struct and the logger.
+	app := &application{
+		config: cfg,
+		logger: logger,
+	}
+
+	/*
+		Declare a new servemux and add a /v1/healthcheck route which dispatches requests
+		to the healthcheckHandler method.
+	*/
+	mux := http.NewServeMux()
+	mux.HandleFunc("/v1/healthcheck", app.healthcheckHandler)
+
+	/*
+		Declare a HTTP server which listens on the port provided in the config struct,
+		uses the servemux we created above as the handler, has some sensible timeout
+		settings and writes any log messages to the structured logger at Error level.
+	*/
+	srv := &http.Server{
+		Addr:         fmt.Sprintf(":%d", cfg.port),
+		Handler:      mux,
+		IdleTimeout:  time.Minute,
+		ReadTimeout:  5 * time.Second,
+		WriteTimeout: 10 * time.Second,
+		ErrorLog:     slog.NewLogLogger(logger.Handler(), slog.LevelError),
+	}
+
+	// Start the HTTP server.
+	logger.Info("starting server", "addr", srv.Addr, "env", cfg.env)
+
+	err := srv.ListenAndServe()
+	if err != nil {
+		logger.Error(err.Error())
+		os.Exit(1)
+	}
+}