go-hotreload

Simple Go app executed in a container with hot reload and dynamic import of a local package.

Description

It is a good practice the run Go application in a Docker container, and use hot reload and local packages for developpment is important.

This app allows to:

• Start a Go application in a Docker container.
• Use hot reload to restart the application each time a file is saved in myapp.
• Import a dynamicly updatable local package from mypackage.

How to use

The application can be executed with the released package or with the local package.

Start with the released package

The application can be executed with the released package on GitHub to preserve compatibility with official packages.

Build image and start app:

cd myapp/
make dev

Or force build image and start app:

cd myapp/
make dev-build

The terminal should display:

Call Package: Hello World from Mypackage

Start with the local package

The application can be executed with the local package to allow dynamic updates on the package.

Build image and start app:

cd myapp/
make dev-local

Or force build image and start app:

cd myapp/
make dev-local-build

The terminal should display:

Call Package: Hello World from Mypackage

Test

Update mypackage

Update mypackage/mytest/mytest.go by changing response message.

Example:

replace message := ... by

message := "Hello World from Mypackage updated"

Update myapp

Update myapp/main.go by changing response message.

Example:

replace message := ... by

message := "Call updated Package:"

When myapp/main.go is saved, the app should rebuild.

If the app is started with make dev or make dev-build, the package is not updated, the terminal should display:

Call updated Package: Hello World from Mypackage

If the app is started with make dev-local or make dev-local-build, the package is dynamically updated, the terminal should display:

Call updated Package: Hello World from Mypackage updated

How it works

Dynamic local package

To use a local package, specify the ./go.dev.mod file in the go mod edit -replace command.

Example:

go mod edit -replace github.com/phoax/go-hotreload/mypackage=../mypackage ./go.dev.mod

Then, when started the go.mod app will be overwritten by go.dev.mod thanks to ../myapp/go.dev.mod:/go/src/myapp/go.mod

docker-compose.yml:

[...]
    volumes:
      [...]
      - ../myapp/go.dev.mod:/go/src/myapp/go.mod

Hot reload

Hot reload is simply enabled by compiling and starting the app with go get github.com/githubnemo/CompileDaemon package.

Dockerfile:

[...]

RUN go get github.com/githubnemo/CompileDaemon

ENTRYPOINT CompileDaemon --build="go build main.go" --command="./main"