chore(Dockerfile): update base image to golang:1.20.6-bullseye and re…

…move unnecessary environment variables

The base image for the Dockerfile has been updated to
golang:1.20.6-bullseye to use a more recent version of Golang. The
environment variables GO111MODULE and CGO_ENABLED have been removed as
they are not needed for the build process.

build/package/Dockerfile

@@ -1,8 +1,7 @@
-FROM golang:1.13.15-buster AS builder
+FROM golang:1.20.6-bullseye AS builder
 LABEL maintainer="Siddhartha Basu <[email protected]>"
 ENV GOPROXY https://proxy.golang.org
-ENV GO111MODULE=on \
-    CGO_ENABLED=0 \
+ENV CGO_ENABLED=0 \
     GOOS=linux \
     GOARCH=amd64
 RUN apt-get -qq update \
@@ -24,9 +23,8 @@ RUN go build \
     -tags netgo \
     -o /bin/app \
     main.go
-RUN strip /bin/app \
-    && upx -q -9 /bin/app
+RUN upx -q -9 /bin/app
 
 FROM gcr.io/distroless/static
 COPY --from=builder /bin/app /usr/local/bin/
-ENTRYPOINT ["/usr/local/bin/app"]
+ENTRYPOINT ["/usr/local/bin/app"]