perf: use multistage build to slim down backend container

Author: lpmi-13

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:latest
+FROM golang:latest AS builder
 
 LABEL app="slo-tracker"
 LABEL maintainer="roshan.aloor@gmail.com"
@@ -8,9 +8,16 @@ LABEL description="slo-tracker : Track your product SLO"
 WORKDIR /app
 
 COPY . .
-RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -o /app/slo-tracker .
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -ldflags "-w -s" -o /app/slo-tracker .
 
 
+FROM scratch
+
+# we don't need these certs for local development, but we copy in case you want
+# to use this image for a production environment
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
+COPY --from=builder /app/slo-tracker /app/slo-tracker
+
 EXPOSE 8080
 
-CMD /app/slo-tracker
+CMD ["/app/slo-tracker"]