Comment by atmosx

A simple multistage example for Golang apps would be:

  FROM golang:1.12.4
  WORKDIR /opt/src/github.com/project1/myprog/
  COPY . .
  RUN go get -d -v ./...
  RUN CGO_ENABLED=0 GOOS=linux go build -a -mod=vendor -o myprog .
  
  FROM ubuntu:latest
  RUN useradd -u 5002 user1
  
  FROM scratch
  COPY --from=0 /opt/src/github.com/project1/myprog/myprog .
  COPY --from=1 /etc/passwd /etc/passwd
  USER user1
  ENTRYPOINT ["./myprog"]