After reading about the enormous image size reductions that are possible with multi-stage docker builds, I'm attempting to slim down the image size for a Dockerfile I have for building a Go binary. My Dockerfile is below.
# Configure environment and build settings.
FROM golang:alpine AS buildstage
ARG name=ddmnh
ENV GOPATH=/gopath
# Create the working directory.
WORKDIR ${GOPATH}
# Copy the repository into the image.
ADD . ${GOPATH}
# Move to GOPATH, install dependencies and build the binary.
RUN cd ${GOPATH} && go get ${name}
RUN CGO_ENABLED=0 GOOS=linux go build ${name}
# Multi-stage build, we just use plain alpine for the final image.
FROM alpine:latest
# Copy the binary from the first stage.
COPY --from=buildstage ${GOPATH}/${name} ./${name}
RUN chmod u+x ./${name}
# Expose Port 80.
EXPOSE 80
# Set the run command.
CMD ./ddmnh
The resulting image, however, doesn't seem to be size reduced at all. I suspect that the golang:alpine image is being included somehow. Below is a screenshot of the results of running docker build . on the Dockerfile above.
The alpine:latest image is only 4.15MB. Adding the size of the compiled binary (which is relatively small) I would expect no more than, say, maybe 15MB for the final image. But it's 407MB. I'm clearly doing something wrong!
How can I adjust my Dockerfile to produce an image of less size?
