feat: vendor, makefiles, build settings

projects/greenlight/cmd/api/main.go

@@ -5,6 +5,7 @@ import (
 	"database/sql"
 	"expvar"
 	"flag"
+	"fmt"
 	"os"
 	"runtime"
 	"strings"
@@ -23,6 +24,10 @@ import (
 // number as a hard-coded global constant.
 const version = "1.0.0"
 
+// Create a buildTime variable to hold the executable binary build time. Note that this
+// must be a string type, as the -X linker flag will only work with string variables.
+var buildTime string
+
 // 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
@@ -120,8 +125,20 @@ func main() {
 		return nil
 	})
 
+	// Create a new version boolean flag with the default value of false.
+	displayVersion := flag.Bool("version", false, "Display version and exit")
+
 	flag.Parse()
 
+	// If the version flag value is true, then print out the version number and
+	// immediately exit.
+	if *displayVersion {
+		fmt.Printf("Version:\t%s\n", version)
+		// Print out the contents of the buildTime variable.
+		fmt.Printf("Build time:\t%s\n", buildTime)
+		os.Exit(0)
+	}
+
 	// Call the openDB() helper function (see below) to create the connection pool,
 	// passing in the config struct. If this returns an error, we log it and exit the
 	// application immediately.