Make listen address configurable

evaluator.go

@@ -4,6 +4,7 @@ import (
 	"log"
 	"net/http"
 	"net/url"
+	"os"
 	"regexp"
 	"strings"
 )
@@ -26,7 +27,22 @@ func main() {
 		http.Redirect(w, r, searchURL, http.StatusSeeOther)
 	})
 
-	log.Fatalf("Failed to start http server: %v", http.ListenAndServe(":8081", nil))
+	listenAddress := getSetting("LISTEN_ADDRESS", ":8081")
+	log.Printf("Listening at %s", listenAddress)
+
+	log.Fatalf("Failed to start http server: %v", http.ListenAndServe(listenAddress, nil))
+}
+
+func getenv(name string, fallback string) (value string) {
+	value = os.Getenv(name)
+	if value == "" {
+		return fallback
+	}
+	return
+}
+
+func getSetting(name, fallback string) (value string) {
+	return getenv("BANG_EVALUATOR_"+name, fallback)
 }
 
 func buildSearchURL(template string, query string) (searchUrl string) {