How to import an unpopular package to Docker using the GOLang official image? - go

Question

I've posted this question already as an issue on the imagick git repository, but it has a very small user-base, so I'm hoping to get some help from here. I've been trying for a few days now to import https://github.com/gographics/imagick to Docker using the official goLang dockerfile for a project I'm working on, but have been unsuccessful. Since this package isn't popular, running apt-get won't work. I've (hesitantly) tried to just add the files to the container, but that didn't work. Here's the DockerFile I've built and the error it produces:
===DOCKERFILE===
# 1) Use the official go docker image built on debian.
FROM golang:latest
# 2) ENV VARS
ENV GOPATH $HOME/<PROJECT>
ENV PATH $HOME/<PROJECT>/bin:$PATH
# 3) Grab the source code and add it to the workspace.
ADD . /<GO>/src/<PROJECT>
ADD . /<GO>/gopkg.in
# Trying to add the files manually... Doesn't help.
ADD . /opt/local/share/doc/ImageMagick-6
# 4) Install revel and the revel CLI.
#(The commented out code is from previous attempts)
#RUN pkg-config --cflags --libs MagickWand
#RUN go get gopkg.in/gographics/imagick.v2/imagick
RUN go get github.com/revel/revel
RUN go get github.com/revel/cmd/revel
# 5) Does not work... Can't find the package.
#RUN apt-get install libmagickwand-dev
# 6) Get godeps from main repo
RUN go get github.com/tools/godep
# 7) Restore godep dependencies
WORKDIR /<GO>/src/<PROJECT>
RUN godep restore
# 8) Install Imagick
#RUN go build -tags no_pkgconfig gopkg.in/gographics/imagick.v2/imagick
# 9) Use the revel CLI to start up our application.
ENTRYPOINT revel run <PROJECT> dev 9000
# 10) Open up the port where the app is running.
EXPOSE 9000
===END DOCKERFILE===
This allows me to build the docker container, but when I try to run it, I get the following error in the logs of kinematic:
===DOCKER ERROR===
ERROR 2016/08/20 21:15:10 build.go:108: # pkg-config --cflags MagickWand MagickCore MagickWand MagickCore
pkg-config: exec: "pkg-config": executable file not found in $PATH
2016-08-20T21:15:10.081426584Z
ERROR 2016/08/20 21:15:10 build.go:308: Failed to parse build errors:
#pkg-config --cflags MagickWand MagickCore MagickWand MagickCore
pkg-config: exec: "pkg-config": executable file not found in $PATH
2016-08-20T21:15:10.082140143Z
===END DOCKER ERROR===

Answer 1

Most base images have package lists removed to avoid to reduce image size. Thus, in order to install something with apt-get, you first need to update the package lists and then install whatever package you wish. Then, after installing the package, remove all side-effects of running apt to avoid polluting the image with unneeded files (all that necessarily as a single RUN command).
The following Dockerfile should do the trick:
FROM golang:latest
RUN apt-get update \ # update package lists
&& apt-get install -y libmagickwand-dev \ # install the package
&& apt-get clean \ # clean package cache
&& rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* # remove everything else
RUN go get gopkg.in/gographics/imagick.v2/imagick
Remember to add -y to apt-get install, because docker build is non-interactive.