Enable multi-architecture docker image builds

Previously, the Dockerfile downloaded 'docker-gen' and 'forego' binaries
during build time. This caused a problem as it hard-coded the amd64
architecture for the images.

This commit updates both 'Dockerfile' and 'Dockerfile.alpine' to build
the `forego` and `docker-gen` executables from scratch instead of
downloading binaries directly.

This is achieved using multi-stage builds [1]. Two seperate stages first
build the binaries, and are then copied over to the final stage.

The advantage of this change is two-fold: First, it enables building
this image on architectures other than amd64. Secondly it adds trust by
not adding external binaries to the docker image.

This modified version passes the test both a linux desktop (amd64) as
well as a raspberry pi (armv7) with some caveats:

- On armv7, a modified version of the `jwilder/docker-gen` image is
required. See a seperate PR at [2].

- The 'test_dhparam_is_generated_if_missing' test fails. This also
doesn't currently pass on master.

[1] https://docs.docker.com/develop/develop-images/multistage-build/ [2]
nginx-proxy/docker-gen#327

Author: tkw1536

Dockerfile

@@ -1,3 +1,42 @@
+# Use a specific version of golang to build both binaries
+FROM golang:1.14 as gobuilder
+
+# Build docker-gen from scratch
+FROM gobuilder as dockergen
+
+# Download the sources for the given version
+ENV DOCKER_GEN_VERSION 0.7.4
+ADD https://github.com/jwilder/docker-gen/archive/${DOCKER_GEN_VERSION}.tar.gz sources.tar.gz
+
+# Move the sources into the right directory
+RUN tar -xzf sources.tar.gz && \
+   mkdir -p /go/src/github.com/jwilder/ && \
+   mv docker-gen-* /go/src/github.com/jwilder/docker-gen
+
+# Install the dependencies and make the docker-gen executable
+WORKDIR /go/src/github.com/jwilder/docker-gen
+RUN go get -v ./... && \
+   CGO_ENABLED=0 GOOS=linux go build -ldflags "-X main.buildVersion=${DOCKER_GEN_VERSION}" ./cmd/docker-gen
+
+# Build forego from scratch
+# Because this relies on golang workspaces, we need to use go < 1.8. 
+FROM gobuilder as forego
+
+# Download the sources for the given version
+ENV FOREGO_VERSION 0.16.1
+ADD https://github.com/jwilder/forego/archive/v${FOREGO_VERSION}.tar.gz sources.tar.gz
+
+# Move the sources into the right directory
+RUN tar -xzf sources.tar.gz && \
+   mkdir -p /go/src/github.com/ddollar/ && \
+   mv forego-* /go/src/github.com/ddollar/forego
+
+# Install the dependencies and make the forego executable
+WORKDIR /go/src/github.com/ddollar/forego/
+RUN go get -v ./... && \
+   CGO_ENABLED=0 GOOS=linux go build -o forego .
+
+# Build the final image
 FROM nginx:1.19.3
 LABEL maintainer="Jason Wilder [email protected]"
 
@@ -14,15 +53,9 @@ RUN apt-get update \
 RUN echo "daemon off;" >> /etc/nginx/nginx.conf \
  && sed -i 's/worker_processes  1/worker_processes  auto/' /etc/nginx/nginx.conf
 
-# Install Forego
-ADD https://github.com/jwilder/forego/releases/download/v0.16.1/forego /usr/local/bin/forego
-RUN chmod u+x /usr/local/bin/forego
-
-ENV DOCKER_GEN_VERSION 0.7.4
-
-RUN wget https://github.com/jwilder/docker-gen/releases/download/$DOCKER_GEN_VERSION/docker-gen-linux-amd64-$DOCKER_GEN_VERSION.tar.gz \
- && tar -C /usr/local/bin -xvzf docker-gen-linux-amd64-$DOCKER_GEN_VERSION.tar.gz \
- && rm /docker-gen-linux-amd64-$DOCKER_GEN_VERSION.tar.gz
+# Install Forego + docker-gen
+COPY --from=forego /go/src/github.com/ddollar/forego/forego /usr/local/bin/forego
+COPY --from=dockergen /go/src/github.com/jwilder/docker-gen/docker-gen /usr/local/bin/docker-gen
 
 COPY network_internal.conf /etc/nginx/
 

Dockerfile.alpine

@@ -1,3 +1,43 @@
+# Use a specific version of golang to build both binaries
+FROM golang:1.14-alpine as gobuilder
+RUN apk add --no-cache git
+
+# Build docker-gen from scratch
+FROM gobuilder as dockergen
+
+# Download the sources for the given version
+ENV DOCKER_GEN_VERSION 0.7.4
+ADD https://github.com/jwilder/docker-gen/archive/${DOCKER_GEN_VERSION}.tar.gz sources.tar.gz
+
+# Move the sources into the right directory
+RUN tar -xzf sources.tar.gz && \
+   mkdir -p /go/src/github.com/jwilder/ && \
+   mv docker-gen-* /go/src/github.com/jwilder/docker-gen
+
+# Install the dependencies and make the docker-gen executable
+WORKDIR /go/src/github.com/jwilder/docker-gen
+RUN go get -v ./... && \
+   CGO_ENABLED=0 GOOS=linux go build -ldflags "-X main.buildVersion=${DOCKER_GEN_VERSION}" ./cmd/docker-gen
+
+# Build forego from scratch
+# Because this relies on golang workspaces, we need to use go < 1.8. 
+FROM gobuilder as forego
+
+# Download the sources for the given version
+ENV FOREGO_VERSION 0.16.1
+ADD https://github.com/jwilder/forego/archive/v${FOREGO_VERSION}.tar.gz sources.tar.gz
+
+# Move the sources into the right directory
+RUN tar -xzf sources.tar.gz && \
+   mkdir -p /go/src/github.com/ddollar/ && \
+   mv forego-* /go/src/github.com/ddollar/forego
+
+# Install the dependencies and make the forego executable
+WORKDIR /go/src/github.com/ddollar/forego/
+RUN go get -v ./... && \
+   CGO_ENABLED=0 GOOS=linux go build -o forego .
+
+# Build the final image
 FROM nginx:1.19.3-alpine
 LABEL maintainer="Jason Wilder [email protected]"
 
@@ -11,15 +51,9 @@ RUN apk add --no-cache --virtual .run-deps \
 RUN echo "daemon off;" >> /etc/nginx/nginx.conf \
  && sed -i 's/worker_processes  1/worker_processes  auto/' /etc/nginx/nginx.conf
 
-# Install Forego
-ADD https://github.com/jwilder/forego/releases/download/v0.16.1/forego /usr/local/bin/forego
-RUN chmod u+x /usr/local/bin/forego
-
-ENV DOCKER_GEN_VERSION 0.7.4
-
-RUN wget --quiet https://github.com/jwilder/docker-gen/releases/download/$DOCKER_GEN_VERSION/docker-gen-alpine-linux-amd64-$DOCKER_GEN_VERSION.tar.gz \
- && tar -C /usr/local/bin -xvzf docker-gen-alpine-linux-amd64-$DOCKER_GEN_VERSION.tar.gz \
- && rm /docker-gen-alpine-linux-amd64-$DOCKER_GEN_VERSION.tar.gz
+# Install Forego + docker-gen
+COPY --from=forego /go/src/github.com/ddollar/forego/forego /usr/local/bin/forego
+COPY --from=dockergen /go/src/github.com/jwilder/docker-gen/docker-gen /usr/local/bin/docker-gen
 
 COPY network_internal.conf /etc/nginx/