Add go packages

src/SUMMARY.md

@@ -5,6 +5,7 @@
 - [Dev](./dev/main.md)
 
   - [Golang](./dev/golang/main.md)
+    - [Packages](./dev/golang/packages.md)
     - [Testing](./dev/golang/testing.md)
   - [Elixir](./dev/elixir/main.md)
     - [Lambda](./dev/elixir/lambda.md)

src/dev/golang/packages.md

@@ -0,0 +1,68 @@
+# Working with packages
+
+In go, every project, is, at some part, a package.
+
+A package is simply a directory containing go source file.
+
+## Organising projects
+
+In your project, you may need multiple, isolated packages. Here is the most
+common project layout in found and I used in all my projects :
+
+```txt
+layout -- top project directory
+├── build -- all things related to ci
+│   └── ci
+│       └── ci.yml
+├── cmd -- main package, entrypoing
+│   └── layout.go
+├── Dockerfile -- container build instructions
+├── init -- if usefull systemd service file
+│   └── layout.service
+├── internal -- private packages, ie not to be used in another project
+│   └── private
+│       └── private.go
+├── LICENSE -- license file
+├── pkg -- public packages, ie packages like libs, to be importer in another project
+│   └── public
+│       └── public.go
+└── README.md -- readme
+```
+
+## Using go mod
+
+Init project
+
+```shell
+go mod init github.com/username/project
+```
+
+### Add an external dep to your project
+
+Import the required package
+
+```go
+import "github.com/example/lib"
+```
+
+The next time you will run a go command it will fetch the package, eg :
+
+```shell
+go build
+```
+
+### In repository packages
+
+Of course, you can also use isolated package you write inside your repository (usefull if you need to split things up)
+
+Let's say, for example, I want to add a new public package `foo` in my project,
+
+```shell
+mkdir -p pkg/foo && echo "package foo" > pkg/foo/foo.go
+```
+
+After adding stuff in your `foo.go` file, import it using
+
+```go
+import "github.com/username/project/foo"
+```