Introduction

This is a project to get the hang of the Go language, Docker containers, continuous integration with CircleCI.

This is built on Ubuntu Xenial (16.04). On Windows/Mac some tweaks probably needed.

Build status:

Origin source

Refer:
https://github.com/halla/golang-docker-circleci-example

Core Todo

• Docker hello world
• Hello http server
• Unit test case
• Development workflow with code reload/compile
• Make a HTTP-request
• Parse JSON
• CircleCI integration
• Production deployment
• Contiuous deployment
• Automated branch in workflow

More Todo

• Use a goroutine
• Use a channel
• Use an HTML template
• Serve static files
• docker-compose.yml

Usage

Development

Assuming you have docker installed, clone this repo, cd to the project directory, build and run:

• $ docker build -t hello-golang .
• $ docker run --volume=$PWD:/go/src/app -p 8080:3000 --rm --name my-running-app hello-golang

You should see "Starting server..." in the console, and "Hello world" in your browser if you navigate to localhost:8080

build -t tags the container with the given name --volume mounts the current directory to the docker container for code reloading -p binds your host port to docker port --rm removes the container after exit --name assigns a name

If you modify the source code, you should see the changes when refreshing your browser window.

Deployment

To deploy the project using the image in Docker Hub registry

• install Docker on your server
• docker pull ahalla/golang-docker-circleci-example
• docker run -d -p 8080:3000 --rm --name golang-docker-circleci-example ahalla/golang-docker-circleci-example

This will run the container as a background job, listening to the OS port 8080. The container will be removed automatically when killed.

Contiuous deployment

To automatically update the running application, you can do something along the lines of:

#/bin/bash
echo "Pulling the latest version from registry"
docker pull ahalla/golang-docker-circleci-example
echo "Killing the running container"
docker kill golang-docker-circleci-example
echo "Preparing to run.."
docker run -d -p 8080:3000 --rm --name golang-docker-circleci-example ahalla/golang-docker-circleci-example

Here we give the container a name so we can kill it later. This script can be either triggered from the CI or run in cron for periodical updates (you should probably add a check whether a new version was actually pulled or not).

This is a naive solution, but probably enough to start with.

Technology links

• The Go Programming Language https://golang.org/
• Docker https://www.docker.com/
• CircleCI https://circleci.com/
• golang docker image https://hub.docker.com/_/golang/
• gin for code reloading https://github.com/codegangsta/gin

Tutorials

• Install Docker on Ubuntu 16.04 https://www.digitalocean.com/community/tutorials/how-to-install-and-use-docker-on-ubuntu-16-04
• Development with Go and Docker https://medium.com/developers-writing/docker-powered-development-environment-for-your-go-app-6185d043ea35

Issue knowledge

1. Fix issue related to Golang version: strings.Builder type undefined

Problem

$ docker build -t hello-golang .

=> Error:
 > [3/7] RUN go get github.com/codegangsta/gin:
#7 10.17 # github.com/urfave/cli
#7 10.17 src/github.com/urfave/cli/fish.go:74:18: undefined: strings.Builder
#7 10.17 src/github.com/urfave/cli/fish.go:123:18: undefined: strings.Builder
#7 10.17 src/github.com/urfave/cli/fish.go:160:45: undefined: strings.Builder

Solution

Because golang version is old, Dockerfile define that:
$ FROM golang:1.9-alpine
To fix it, change golang to new version:
$ FROM golang:1.15-alpine

Note:

alpine is a feature to caching memory.
To use it, it is used by command in Dockerfile

RUN apk add --no-cache git

Refer:

  https://stackoverflow.com/questions/48978414/golang-strings-builder-type-undefined  

2. Fix issue related to GIN library.

Problem

$ docker build -t hello-golang .

=> [1/7] FROM docker.io/library/golang:1.15-alpine@sha256:b58c367d52e46cdedc25ec9cd74cadb14ad65e8db75b25e5ec117c  0.0s
=> CACHED [2/7] RUN apk add --no-cache git                                                                        0.0s
=> ERROR [3/7] RUN go get github.com/codegangsta/gin                                                             13.0s
------
 > [3/7] RUN go get github.com/codegangsta/gin:
#6 12.99 # github.com/codegangsta/gin
#6 12.99 src/github.com/codegangsta/gin/main.go:40:13: cannot use MainAction (type func(*cli.Context)) as type cli.ActionFunc in assignment
#6 12.99 src/github.com/codegangsta/gin/main.go:42:17: cannot use cli.StringFlag literal (type cli.StringFlag) as type cli.Flag in slice literal:
#6 12.99        cli.StringFlag does not implement cli.Flag (Apply method has pointer receiver)

Solution

Because we are using codegangta library from github: https://github.com/codegangsta/gin It always changing content of source code, unfortunately, it happened this error.
Therefore, I must following issue on that repository, and we find this issue following info below

Before: 
# Gin for code reloading
RUN go get github.com/codegangsta/gin

After:
# Gin for code reloading
RUN go get github.com/kisielk/errcheck \
    && go get golang.org/x/lint/golint \
    && go get github.com/stripe/safesql \
    && GO111MODULE=on go get github.com/gobuffalo/buffalo/[email protected]

Refer:

https://github.com/codegangsta/gin/issues/169

3. Fix issue related to run command on Docker virtual machine.

Problem

$ docker build -t hello-golang .

=> ERROR [6/7] RUN go-wrapper download # "go get -d -v ./..."
------
 > [6/7] RUN go-wrapper download # "go get -d -v ./...":
#11 0.328 /bin/sh: go-wrapper: not found
------
executor failed running [/bin/sh -c go-wrapper download # "go get -d -v ./..."]: exit code: 127

Solution

Before: 
RUN go-wrapper download # "go get -d -v ./..."
RUN go-wrapper install # "go install -v ./..."

After:
RUN go get -d -v ./...
RUN go install -v ./...

Refer:

https://github.com/whalebrew/whalebrew/commit/2495345eadd7b1860a3557c81f203619d9b84ea8