Add Dockerfile so apg-go can be dockerized via Github

Dockerfile

@@ -0,0 +1,19 @@
+## Build first
+FROM golang:latest as builder
+RUN mkdir /builddir
+ADD . /builddir/
+WORKDIR /builddir
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -a -installsuffix cgo -ldflags '-w -s -extldflags "-static"' -o apg-go \
+    github.com/wneessen/apg-go/cmd/apg
+
+## Create scratch image
+FROM scratch
+LABEL maintainer="wn@neessen.net"
+COPY ["docker-files/passwd", "/etc/passwd"]
+COPY ["docker-files/group", "/etc/group"]
+COPY --chown=apg-go ["LICENSE", "/apg-go/LICENSE"]
+COPY --chown=apg-go ["README.md", "/apg-go/README.md"]
+COPY --from=builder --chown=apg-go ["/builddir/apg-go", "/apg-go/apg-go"]
+WORKDIR /apg-go
+USER apg-go
+ENTRYPOINT ["/apg-go/apg-go"]

README.md

@@ -12,6 +12,19 @@ Since FIPS-181 (pronouncable passwords) has been withdrawn in 2015, apg-go does
 it implements the [Koremutake Syllables System](https://shorl.com/koremutake.php) in its pronouncable password mode.
 
 ## Installation
+
+### Docker
+There is a ready-to-use Docker image hosted on Github.
+
+* Download the image:
+  ```shell
+  $ docker pull ghcr.io/wneessen/apg-go:main
+  ```
+* Run the image:
+  ```shell
+  $ docker run ghcr.io/wneessen/apg-go:main
+  ```
+
 ### Ports/Packages
 #### FreeBSD
 apg-go can be found as `/security/apg` in the [FreeBSD ports](https://cgit.freebsd.org/ports/tree/security/apg)

docker-files/group

@@ -0,0 +1 @@
+apg-go:*:1000:apg-go

docker-files/passwd

@@ -0,0 +1 @@
+apg-go:*:1000:1000:Automated Password Generator User:/apg-go:/usr/bin/false