Add code from PR amitshekhariitbhu#4 - Minify and secure docker image

Author: Yuri-SN

Dockerfile

@@ -1,11 +1,13 @@
-FROM golang:1.19-alpine
-
-RUN mkdir /app
-
-ADD . /app
-
-WORKDIR /app
-
-RUN go build -o main cmd/main.go
-
-CMD ["/app/main"]
+FROM golang:1.19-alpine as builder
+WORKDIR /
+COPY go.mod .
+RUN go mod download
+COPY . .
+RUN mkdir exec
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -a -o exec/main cmd/main.go
+
+FROM gcr.io/distroless/static:nonroot
+WORKDIR /
+COPY --from=builder /exec /app
+USER 65532:65532
+ENTRYPOINT ["/app/main"]