Go Multistage Dockerfile builder

Go: Multistage Docker build

# Builder stage
FROM golang:1.9 AS builder
LABEL MAINTAINER "Team Name <team@email.com>"

# Install tools required to build the project
RUN go get github.com/golang/dep/cmd/dep

# Add ssh key to clone private repos
ARG SSH_PRIVATE_KEY
COPY ${SSH_PRIVATE_KEY} /root/.ssh/id_rsa
RUN echo "[url \"git@gitlab.com:\"]\n\tinsteadOf = https://gitlab.com/" >> /root/.gitconfig \
    && echo "StrictHostKeyChecking no " > /root/.ssh/config \
    && chmod 600 /root/.ssh/id_rsa

# Gopkg.toml and Gopkg.lock lists project dependencies
# These layers are only re-built when Gopkg files are updated
WORKDIR /go/src/gitlab.com/repo
COPY Gopkg.toml Gopkg.lock ./
# Install library dependencies
RUN dep ensure -v --vendor-only

# Copy all project and build it
# This layer is rebuilt when ever a file has changed in the project directory
COPY . ./
RUN CGO_ENABLED=0 GOOS=linux go install ./...

# Production build stage
FROM alpine:3.7
LABEL MAINTAINER "Team Name <team@email.com>"
RUN apk update && apk add ca-certificates mailcap && rm -rf /var/cache/apk/*
EXPOSE 8080
WORKDIR /usr/bin
COPY --from=builder /go/bin .
ENTRYPOINT [ "./binaryName" ]
CMD ["--help"]

docker build --build-arg SSH_PRIVATE_KEY=$(SSH_PRIVATE_KEY) -t $(NAME):$(VERSION) -f $(BUILD_PATH)/$(DOCKERFILE) $(BUILD_PATH)