Add Docker build

Signed-off-by: Knut Ahlers <knut@ahlers.me>

Dockerfile

@@ -0,0 +1,27 @@
+FROM golang:alpine as builder
+
+COPY . /go/src/github.com/Luzifer/webtts
+WORKDIR /go/src/github.com/Luzifer/webtts
+
+RUN set -ex \
+ && apk add --update git \
+ && go install \
+      -ldflags "-X main.version=$(git describe --tags --always || echo dev)" \
+      -mod=readonly
+
+FROM alpine:latest
+
+LABEL maintainer "Knut Ahlers <knut@ahlers.me>"
+
+RUN set -ex \
+ && apk --no-cache add \
+      ca-certificates
+
+COPY --from=builder /go/bin/webtts /usr/local/bin/webtts
+
+EXPOSE 3000
+
+ENTRYPOINT ["/usr/local/bin/webtts"]
+CMD ["--"]
+
+# vim: set ft=Dockerfile: