Add INSTANCE_ID env port offset

src/main.go

@@ -74,9 +74,15 @@ func init() {
 func main() {
 	defer r.Close()
 
-	log.Printf("Listening on %s:%d\n", conf.Host, conf.Port)
+	instanceID, err := GetInstanceID()
 
-	if err := app.Listen(fmt.Sprintf("%s:%d", conf.Host, conf.Port)); err != nil {
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	log.Printf("Listening on %s:%d\n", conf.Host, conf.Port+instanceID)
+
+	if err := app.Listen(fmt.Sprintf("%s:%d", conf.Host, conf.Port+instanceID)); err != nil {
 		log.Fatalf("failed to start server: %v", err)
 	}
 }

src/util.go

@@ -6,7 +6,9 @@ import (
 	"encoding/hex"
 	"fmt"
 	"io"
+	"log"
 	"net/http"
+	"os"
 	"regexp"
 	"strconv"
 	"strings"
@@ -124,6 +126,21 @@ func ParseAddress(address string, defaultPort uint16) (string, uint16, error) {
 	return result[0], uint16(port), nil
 }
 
+// GetInstanceID returns the INSTANCE_ID environment variable parsed as an unsigned 16-bit integer.
+func GetInstanceID() (uint16, error) {
+	if instanceID := os.Getenv("INSTANCE_ID"); len(instanceID) > 0 {
+		value, err := strconv.ParseUint(instanceID, 10, 16)
+
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		return uint16(value), nil
+	}
+
+	return 0, nil
+}
+
 // PointerOf returns a pointer of the argument passed.
 func PointerOf[T any](v T) *T {
 	return &v