Add Docker configuration

Dockerfile

@@ -0,0 +1,9 @@
+FROM golang:1.16-alpine as build
+WORKDIR /go/src/app
+COPY . /go/src/app
+RUN CGO_ENABLED=0 go build -o /go/bin/app
+
+FROM gcr.io/distroless/base-debian10
+LABEL maintainer="Luke Tainton <luke@tainton.uk>"
+COPY --from=build /go/bin/app /
+CMD ["/app"]