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Containerize This! How to build Golang Dockerfiles

Adapted from this blog post.

Building

Run the below docker build command lines from within each of the respective sub-directories.

Single-stage

cd 1.0-single
docker build --tag hello-docker-main:1.0 .

Multi-stage

cd 1.1-multi
docker build --tag hello-docker-main:1.1 .

FROM scratch

cd 1.2-scratch
docker build --tag hello-docker-main:1.2 .

Checking

The docker images command (with a repository filter) will show the built images.

$ make show
docker images hello-docker-main
REPOSITORY          TAG   IMAGE ID       CREATED         SIZE
hello-docker-main   1.0   ee418f55f5bf   4 minutes ago   313MB
hello-docker-main   1.1   6ecb3fc7af82   4 minutes ago   6.32MB
hello-docker-main   1.2   dee372c86f13   4 minutes ago   1.9MB

Take note of how much smaller the 1.1 and 1.2 images are, compared to the initial 1.0.

This is thanks to the use of multiple stages!

1.1 builds in one stage and then copies the built executable into a fresh new stage.

1.2 takes this one step further, and executes in a completely bare second stage which comes from scratch.

Running

Run these docker run command lines to execute the built images.

1.0

$ docker run hello-docker-main:1.0
Hello Docker v1.0!

1.1

$ docker run hello-docker-main:1.1
Hello Docker v1.1!

1.2

$ docker run hello-docker-main:1.2
Hello Docker v1.2!