rebuy-go-sdk

Library for our Golang projects

Development Status rebuy-go-sdk is designed for internal use. Since it uses Semantic Versioning it is safe to use, but expect big changes between major version updates.

Application Layout

General Directory Structure

Please take a look at the examples directory to see how it actually looks like.

/
├── cmd/[subcommand/]
│   ├── `root.go`
│   └── `...`
├── `pkg/`
│   ├── `app/...`
│   ├── `dal/...`
│   ├── `bll/...`
│   └── `...`
├── `buildutil`
├── `go.mod`
├── `go.sum`
├── `LICENSE`
├── `main.go`
├── `README.md`
└── `tools.go`

• /buildutil is a convenience wrapper to execute the buildutil command from the SDK. It ensures that the application gets built with a defined version of buildutil.
• /main.go is the entrypoint of the application and delegates the execution to the Cobra specific functions in /cmd.
• /tools.go forces dependency management of modules, that are not directly imported. This is important for go run and go generate that use external modules. See wiki for more details.
• /cmd/root.go contains the definition for all Cobra commands and the Runners (see below) of the application.
• /pkg/app contains separate components of the application. The /pkg/app directory serves basically the same purpose as the /cmd, but is separated into multiple sub-packages. This is useful when the /cmd directory grows too big and contains components that are mostly independent from each other. How the sub packages of /pkg/app are designed is highly dependent on the application. It could be split model-based (eg users, projects, ...) or it could be split purpose-based (eg web, controllers, ...).
• /pkg/bll stands for "business logic layer" and contains sub-packages that solve a specific use-case of the application.
• /pkg/dal stands for "data access layer" and contains sub-packages that serve as a wrapper for external services and APIs. The idea of grouping such packages is to make their purpose clear and to avoid mixing access to external services with actual business logic.

Runners

Runners are structs that defines command line flags and prepare that application for launch.

The definition of the flags happen in a function typically called Bind with the signature func(cmd *cobra.Command) error:

func (r *Runner) Bind(cmd *cobra.Command) error {
	cmd.PersistentFlags().StringVar(
		&r.name, "name", "World",
		`Your name.`)
	return nil
}

The launch preparation happens in functions with the signature func(ctx context.Context, cmd *cobra.Command, args []string. There can be multiple function for different environments (eg Default, Dev, Staging). The advantage of having multiple functions is that it is easy to setup services in a environment specific way. For example while the default settings use the normal Redis client and use files from go:embed, the dev settings could setup a miniredis instance and open files directly from the file system to avoid having to restart the server on HTML template changes.

See examples/full/cmd/root.go for a typical implementation.

The purpose of splitting the Runner and the actual application code is:

• to get initializing errors as fast as possible (eg if the Redis server is not available),
• to be able to execute environment-specific code without having to use conditionals all over the code-base,
• to be able to mock services for local development
• and to define a proper interface for the application launch, which is very helpful for e2e tests.

Major Release Notes

Note: vN is the new release (eg v3) and vP is the previous one (eg v2).

1. Create a new branch release-vN to avoid breaking changes getting into the previous release.
2. Do your breaking changes in the branch.
3. Update the imports everywhere:
   • find . -type f -exec sed -i 's#github.com/rebuy-de/rebuy-go-sdk/vO#github.com/rebuy-de/rebuy-go-sdk/vP#g' {} +
4. Merge your branch.
5. Add Release on GitHub.