- use `tools.go` to keep tools (like `golangci-lint` and `gox`) dependencies
- see e.g. [https://github.com/golang/go/wiki/Modules#how-can-i-track-tool-dependencies-for-a-module](https://github.com/golang/go/wiki/Modules#how-can-i-track-tool-dependencies-for-a-module)
- see e.g. [https://github.com/golang/go/wiki/Modules#how-can-i-track-tool-dependencies-for-a-module](https://github.com/golang/go/wiki/Modules#how-can-i-track-tool-dependencies-for-a-module)