Update Dockerfile

* Updated base image to Alpine 3.4.
* `codeclimate-golint` binary is built inside the container. You don't
  need go on your machine any more to build the image.
* Updated README to reflect the change. Also gocx is sort of deprecated
  since go is good at crosscompiling now. Moreover, it's not needed any
  more because source is compiled to image-native binary.

Author: pointlessone

Dockerfile

@@ -1,14 +1,21 @@
-FROM alpine:3.2
+FROM alpine:3.4
 
 MAINTAINER Code Climate <hello@codeclimate.com>
 
-WORKDIR /code
+WORKDIR /usr/src/app
+COPY codeclimate-golint.go /usr/src/app
 
-COPY build/codeclimate-golint /usr/src/app/
+RUN apk --update add go git && \
+  export GOPATH=/tmp/go GOBIN=/usr/local/bin && \
+  go get -d . && \
+  go install codeclimate-golint.go && \
+  apk del go git && \
+  rm -rf "$GOPATH" rm /var/cache/apk/*
 
+WORKDIR /code
 VOLUME /code
 
 RUN adduser -u 9000 -D app
 USER app
 
-CMD ["/usr/src/app/codeclimate-golint"]
+CMD ["/usr/local/bin/codeclimate-golint"]

README.md

@@ -27,12 +27,7 @@ engines:
 
 ### Building
 
-In order to build the docker image, you first need to compile a binary for the container. To do that, first [install goxc]() and then run
-
 ```console
-goxc -bc="linux" -tasks-=go-install,go-vet,go-test,package,archive -d=. -arch=amd64 && \
-mv snapshot/linux_amd64/codeclimate-golint bin/codeclimate-golint && \
-rm -rf snapshot && \
 docker build -t codeclimate/codeclimate-golint .
 ```