Create a Dockerfile for a Go application that uses multi-stage builds to reduce the final image size

Question

Create a Dockerfile for a Go application that uses multi-stage builds to reduce the final image size. The application should print “Hello Docker”. Sample Go code.

app.go

package main
 
import "fmt"
 
func main() {
    fmt.Println("Hello Docker")
}

Solution

Dockerfile

FROM golang:1.21.0-alpine

WORKDIR /app

COPY app.go /app
CMD ["go", "run", "app.go"]

Build the image,

docker build -f Dockerfile -t go_image:v1.1.0 .

docker run go_image:v1.1.0

This is a normal image, When we dive into it we can see its 221MB

Let's try using the multistage build,

FROM golang:1.21.0-alpine AS build
WORKDIR /app
COPY app.go .
RUN go build -o myapp app.go

FROM alpine:3.18
WORKDIR /app
COPY --from=build /app/myapp .
CMD ["./myapp"]

Build the image,

docker build -f Dockerfile -t go_image_multi_stage_build:v1.1.0 .

Let's dive into the image,

Now we can see its been reduced from 221MB to 9.2MB.