Using multi-stage builds in Dockerfile

Create some project directories:

cd ~/
mkdir efficient
mkdir inefficient
cd inefficient

Create the source code file:

vi helloworld.go

package main
import "fmt"
func main() {
    fmt.Println("hello world")
}

Create the Dockerfile:

vi Dockerfile

FROM golang:1.12.4
WORKDIR /helloworld
COPY helloworld.go .
RUN GOOS=linux go build -a -installsuffix cgo -o helloworld .
CMD ["./helloworld"]

Build and test the inefficient image:

docker build -t inefficient .
docker run inefficient
docker image ls

Switch to the efficient project directory and copy the files from the inefficient project:
```
cd ~/efficient
cp ../inefficient/helloworld.go ./
cp ../inefficient/Dockerfile ./
```

Change the Dockerfile to use a multi-stage build:

vi Dockerfile

FROM golang:1.12.4 AS compiler
WORKDIR /helloworld
COPY helloworld.go .
RUN GOOS=linux go build -a -installsuffix cgo -o helloworld .

FROM alpine:3.9.3
WORKDIR /root
COPY --from=compiler /helloworld/helloworld .
CMD ["./helloworld"]

Build and test the efficient image:

docker build -t efficient .
docker run efficient
docker image ls

Checkout the size of both images

Using multi-stage builds in Dockerfile

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