docker: build binary in Docker

Signed-off-by: Nicolas Froger <nicolas@kektus.xyz>

.dockerignore

@@ -1,7 +1,4 @@
 .vscode
 .git
-go.mod
-go.sum
-*.go
 helm
 .*ignore

Dockerfile

@@ -1,19 +1,35 @@
-FROM alpine:3.11.6
+FROM golang:1.18.5 as builder
 
 ARG GOOS="linux"
 ARG GOARCH="amd64"
 
+WORKDIR /workspace
+
+COPY go.mod go.sum /workspace/
+
+RUN go mod download
+
+COPY . .
+RUN CGO_ENABLED=0 go build -a -o hugo-mx-gateway
+
+
+FROM alpine:3.16.2
+
 ARG RUNTIME_USER="mxgateway"
 ARG RUNTIME_USER_UID=4583
 
+RUN apk update && apk add --no-cache ca-certificates
+
 RUN addgroup -g $RUNTIME_USER_UID $RUNTIME_USER && \
-    adduser --disabled-password --no-create-home  --gecos "" \
+    adduser --disabled-password --no-create-home --gecos "" \
     --home /app --ingroup $RUNTIME_USER --uid $RUNTIME_USER_UID  $RUNTIME_USER
 
-COPY entrypoint.sh bin/hugo-mx-gateway  LICENSE /app/
+WORKDIR /app
+
+COPY --from=builder /workspace/hugo-mx-gateway .
+COPY entrypoint.sh LICENSE /app/
 COPY templates /app/templates
 
 RUN chown -R $RUNTIME_USER:$RUNTIME_USER /app
 
-WORKDIR /app
 ENTRYPOINT ["sh", "./entrypoint.sh"]