Optmized Dockerfile for golang projects

Dockerfile

FROM golang:1.15.3 AS build
WORKDIR /src
COPY . .
# Dont run your programs as root.
RUN useradd -u 10001 nonprivuser
# CGO_ENABLED=0    -Disable CGO to discard CGO stuff and completely use pure Go net stack.
# -trimpath        -Skip your local paths in error stacktraces, take only from the root of the repo.
# -ldflags="-s -w" -Skip debugging symbol table (DWARF tables) from the binary. About ~25 % less of weight.
# -tags timetzdata -Add tzdata for be docker image indepent. Around ~800KB more size.
RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -tags timetzdata -o my-binary
​
FROM scratch
# Copy CA certificates from build image.
COPY --from=build /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
# Copy users table from build image
COPY --from=build /etc/passwd /etc/passwd
# Copy binary build image
COPY --from=build /src/my-binary /app/my-binary
​
EXPOSE 8080
USER nonprivuser
WORKDIR /app
CMD ["./my-binary"]