add configuration to use traefik-golang sample with Docker Dev Environments feature (#254)

* add configuration to use traefik-golang sample with Docker Dev Environments feature
* use apt-get instead of apt and --no-install-recommends option

Co-authored-by: Milas Bowman <milasb@gmail.com>
Signed-off-by: Guillaume Lours <guillaume.lours@docker.com>

traefik-golang/backend/Dockerfile

@@ -1,9 +1,27 @@
-FROM golang:1.13 AS build
+# syntax=docker/dockerfile:1.4
+
+FROM --platform=$BUILDPLATFORM golang:1.18 AS build
 
 WORKDIR /compose/hello-docker
 COPY main.go main.go
 RUN CGO_ENABLED=0 go build -o backend main.go
 
+FROM build as dev-envs
+
+RUN <<EOF
+apt-get update
+apt-get install -y --no-install-recommends git
+EOF
+
+RUN <<EOF
+useradd -s /bin/bash -m vscode
+groupadd docker
+usermod -aG docker vscode
+EOF
+# install Docker tools (cli, buildx, compose)
+COPY --from=gloursdocker/docker / /
+CMD ["go", "run", "main.go"]
+
 FROM scratch
 COPY --from=build /compose/hello-docker/backend /usr/local/bin/backend
 CMD ["/usr/local/bin/backend"]