make docker image much smaller

.dockerignore

@@ -0,0 +1 @@
+Dockerfile

Dockerfile

@@ -1,19 +1,39 @@
+FROM golang:alpine as builder
+
+RUN apk add --no-cache \
+        build-base \
+        opus-dev
+
+COPY . /go/src/github.com/matthieugrieger/mumbledj
+WORKDIR /go/src/github.com/matthieugrieger/mumbledj
+
+RUN go get -v \
+    && go build -v -ldflags="-s -w"
+
 FROM alpine
 
-ENV GOPATH=/
+RUN adduser -D mumbledj
 
-RUN apk add --update ca-certificates go ffmpeg make build-base opus-dev python aria2
+RUN apk add --no-cache \
-RUN apk upgrade
+        aria2 \
+        libressl \
+        python2
 
-RUN wget https://yt-dl.org/downloads/latest/youtube-dl -O /bin/youtube-dl && chmod a+x /bin/youtube-dl
+RUN wget -O /usr/bin/youtube-dl https://yt-dl.org/downloads/latest/youtube-dl \
+    && chmod +x /usr/bin/youtube-dl
 
-COPY . /src/github.com/matthieugrieger/mumbledj
+RUN wget https://johnvansickle.com/ffmpeg/builds/ffmpeg-git-amd64-static.tar.xz \
-COPY config.yaml /root/.config/mumbledj/config.yaml
+    && tar xvf ffmpeg-git-amd64-static.tar.xz '*/ffmpeg' || true \
+    && mv ffmpeg-git-20190527-amd64-static/ffmpeg /usr/bin/ffmpeg \
+    && rm -rf ffmpeg-git-* \
+    && apk add --no-cache upx \
+    && upx /usr/bin/ffmpeg \
+    && apk del upx
 
-WORKDIR /src/github.com/matthieugrieger/mumbledj
+COPY --from=builder /go/src/github.com/matthieugrieger/mumbledj/mumbledj /usr/bin/mumbledj
 
-RUN make
+COPY config.yaml /home/mumbledj/.config/mumbledj/config.yaml
-RUN make install
-RUN apk del go make build-base && rm -rf /var/cache/apk/*
 
-ENTRYPOINT ["/usr/local/bin/mumbledj"]
+USER mumbledj
+
+ENTRYPOINT ["/usr/bin/mumbledj"]