Make the listen address configurable and allow unix domain socket and inetd style listeners

main.go

@@ -4,8 +4,10 @@ import (
 	"encoding/json"
 	"io"
 	"log"
+	"net"
 	"net/http"
 	"os"
+	"strings"
 	"sync"
 
 	"github.com/gorilla/websocket"
@@ -120,5 +122,34 @@ func main() {
 			}
 		}
 	})
-	log.Println(http.ListenAndServe(":8080", mux))
+
+	var addr string
+	if env, ok := os.LookupEnv("FANCYN_LISTEN"); ok {
+		addr = env
+	} else {
+		addr = "[::1]:8080"
+	}
+	var listener net.Listener
+	if addr == "inetd" {
+		if l, err := net.FileListener(os.Stdin); err == nil {
+			listener = l
+		} else {
+			log.Fatal(err)
+		}
+	} else if strings.HasPrefix(addr, "unix:") {
+		if l, err := net.Listen("unix", strings.TrimPrefix(addr, "unix:")); err == nil {
+			listener = l
+		} else {
+			log.Fatal(err)
+		}
+	} else {
+		if l, err := net.Listen("tcp", addr); err == nil {
+			listener = l
+		} else {
+			log.Fatal(err)
+		}
+	}
+	defer listener.Close()
+	log.Printf("Starting server on %s\n", addr)
+	log.Println(http.Serve(listener, mux))
 }