go + dockerでホットリロード機能を付ける

DockerでGo言語の開発環境を作る方法でDocker+goの開発環境を作りました。今回はさらにホットリロード機能をつけていきます。

Dockerfileを修正

まず、Dockerfileに変更を加えていきます。Dockerfileの中身は以下の記事で取り上げたものをベースにしています。

FROM golang:1.19.1-alpine3.16![スクリーンショット 2023-07-08 202755.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/3439167/54c6704b-3ded-2479-6c9e-b478adf86990.png)


WORKDIR /app

COPY backend/go.mod .
COPY backend/go.sum .
COPY backend/*air.toml .

RUN go mod download
RUN apk add --no-cache gcc
RUN apk add --no-cache musl-dev

COPY ./backend .

RUN go install github.com/cosmtrek/air@latest

CMD ["air"]
# CMD ["go", "run", "./cmd/api"]

.air.tomlを作成

次に以下の場所に.air.tomlを作成します。

project
├backend
│ └Dockerfile
│ └.air.toml　←新規作成
│ └cmd/
│ 　└─api/
│ 　　└─main.go
└docker-compose.yml

.air.tomlは以下のとおりです。

# .air.toml
# Config file for [Air](https://github.com/cosmtrek/air) in TOML format

# Working directory
# . or absolute path, please note that the directories following must be under root.
root = "."
tmp_dir = "tmp"

[build]
# Just plain old shell command. You could use `make` as well.
cmd = "go build -o ./tmp/main ./cmd/api"
# Binary file yields from `cmd`.
bin = "tmp/main"
# Customize binary.
full_bin = "APP_ENV=dev APP_USER=air ./tmp/main"
# Watch these filename extensions.
include_ext = ["go", "tpl", "tmpl", "html"]
# Ignore these filename extensions or directories.
exclude_dir = ["assets", "tmp", "vendor"]
# Watch these directories if you specified.
include_dir = []
# Exclude files.
exclude_file = []
# This log file places in your tmp_dir.
log = "air.log"
# It's not necessary to trigger build each time file changes if it's too frequent.
delay = 1000 # ms
# Stop running old binary when build errors occur.
stop_on_error = true
# Send Interrupt signal before killing process (windows does not support this feature)
send_interrupt = false
# Delay after sending Interrupt signal
kill_delay = 500 # ms

[log]
# Show log time
time = false

[color]
# Customize each part's color. If no color found, use the raw app log.
main = "magenta"
watcher = "cyan"
build = "yellow"
runner = "green"

[misc]
# Delete tmp directory on exit
clean_on_exit = true

以上で準備は終了です。

起動する

以下のとおりのコマンドを実行します。

docker compose build

docker compose up

以下のような表示がされれば成功です。

参考資料