From a6e929541ffffe1bd37064cb0e627ca6be1acd2b Mon Sep 17 00:00:00 2001
From: Grégoire Duchêne <gduchene@awhk.org>
Date: Fri, 10 Apr 2020 00:15:21 +0100
Subject: Allow ADDR to be a path to a UNIX socket

---
 README.md       |  4 ++++
 cmd/gcp/main.go | 28 +++++++++++++++++++++++-----
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/README.md b/README.md
index ca9464e..6c97d53 100644
--- a/README.md
+++ b/README.md
@@ -17,3 +17,7 @@ Additionally, the version under `gcp/` will use:
 * `PORT` for the port to listen on, defaulting to 8080.
 
 See https://golang.org/pkg/net/#Dial for details of the address format.
+
+If `ADDR` is set and starts with `/`, go-import-redirect will treat it
+as the path of a UNIX socket to create and listen on. `PORT` is also
+ignored.
diff --git a/cmd/gcp/main.go b/cmd/gcp/main.go
index 80f3114..c284bbc 100644
--- a/cmd/gcp/main.go
+++ b/cmd/gcp/main.go
@@ -8,6 +8,7 @@ package main
 import (
 	"context"
 	"log"
+	"net"
 	"net/http"
 	"os"
 	"os/signal"
@@ -45,12 +46,29 @@ func main() {
 	signal.Notify(done, os.Interrupt, syscall.SIGINT, syscall.SIGTERM)
 
 	go func() {
-		port := os.Getenv("PORT")
-		if port == "" {
-			port = "8080"
+		var (
+			addr = os.Getenv("ADDR")
+			l    net.Listener
+			err  error
+		)
+		if addr != "" && addr[0] == '/' {
+			if l, err = net.Listen("unix", addr); err != nil {
+				log.Fatalln("net.Listen:", err)
+			}
+			// We do not do any authorization anyway, so 0666 makes sense here.
+			if err = os.Chmod(addr, 0666); err != nil {
+				log.Fatalln("os.Chmod:", err)
+			}
+		} else {
+			port := os.Getenv("PORT")
+			if port == "" {
+				port = "8080"
+			}
+			if l, err = net.Listen("tcp", os.Getenv("ADDR")+":"+port); err != nil {
+				log.Fatalln("net.Listen:", err)
+			}
 		}
-		srv.Addr = os.Getenv("ADDR") + ":" + port
-		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+		if err = srv.Serve(l); err != nil && err != http.ErrServerClosed {
 			log.Fatalln("server.ListenAndServe:", err)
 		}
 	}()
-- 
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