Make docker image smaller, add SHELLIP configuration

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.21.6
+FROM golang:1.21.6 as build
 
 WORKDIR /app
 
@@ -13,9 +13,13 @@ COPY util ./util
 COPY views ./views
 
 EXPOSE 5566 
-RUN go build .
+RUN CGO_ENABLED=0 go build .
+
+FROM alpine as main
+COPY --from=build /app /app
 
 ARG PASSWORD
 ENV PASSWORD $PASSWORD
+WORKDIR /app
 
 ENTRYPOINT ["/app/ezcat"]

README.md

@@ -13,6 +13,16 @@ docker run --rm --network host \
 or you can download the latest binary from the [releases tab](https://github.com/ngn13/ezcat/releases),
 extract it with `tar` and then copy it to somewhere in your `PATH`.
 
+By default ezcat will try to detect your interface IP address (giving priority to tunnel interfaces).
+If you want set this IP address to something else by default, you can use the `SHELLIP` environment variable:
+```
+docker run --rm --network host \
+    -e PASSWORD=securepassword \
+    -e SHELLIP=10.10.10.15     \
+    ghcr.io/ngn13/ezcat
+
+```
+
 ---
 
 ### ⚒️ Build

util/util.go

@@ -4,6 +4,7 @@ import (
 	"encoding/base64"
 	"math/rand"
 	"net"
+	"os"
 	"strings"
 
 	"github.com/gofiber/fiber/v2"
@@ -78,6 +79,11 @@ func GetAddr(addrs []net.Addr) string {
 }
 
 func GetIP() string {
+  enip := os.Getenv("SHELLIP")
+  if enip != "" {
+    return enip
+  }
+
   ip := "127.0.0.1"
   foundtun := false
   ifs, err := net.Interfaces()