✨ Allow setting the listen port via an env variable

.env.sample

@@ -1,4 +1,9 @@
 # Enter the MAC Address of the TP-Link switch
 # you want to monitor here
 
-TPLINK_MAC=ff:ff:ff:ff:ff:ff
+TPLINK_MAC=ff:ff:ff:ff:ff:ff
+
+# The port to bind the Prometheus HTTP server on
+# (default: 9717)
+
+LISTEN_PORT=9717

main.go

@@ -4,7 +4,6 @@ import (
 	"log"
 	"net/http"
 	"os"
-	"strconv"
 
 	"github.com/joho/godotenv"
 	"github.com/prometheus/client_golang/prometheus"
@@ -18,8 +17,11 @@ func main() {
 
 	var (
 		switchMac = os.Getenv("TPLINK_MAC")
-		port      = 9717
+		port      = os.Getenv("LISTEN_PORT")
 	)
+	if port == "" {
+		port = "9717"
+	}
 	if switchMac == "" {
 		log.Fatal("Env variable 'TPLINK_MAC' not set!")
 	}
@@ -36,7 +38,7 @@ func main() {
 
 	// Start Web-Server
 	http.Handle("/metrics", promhttp.Handler())
-	log.Printf("Listening on http://0.0.0.0:%d", port)
-	log.Fatal(http.ListenAndServe(":"+strconv.Itoa(port), nil))
+	log.Printf("Listening on http://0.0.0.0:%s", port)
+	log.Fatal(http.ListenAndServe(":"+port, nil))
 
 }