docs: add docs to featuers (#179)

* docs: add docs to featuers

Signed-off-by: Kasper J. Hermansen <kah@lunar.app>

* feat: with golang example in readme

Signed-off-by: Kasper J. Hermansen <kah@lunar.app>

---------

Signed-off-by: Kasper J. Hermansen <kah@lunar.app>

README.md

@@ -109,6 +109,30 @@ plan: git://git@github.com:lunarway/station-plan.git
 - Write templates in plans and overwrite them in projects when they defer
 - ...
 
+### Golang actions 
+
+Execute golang directly from shuttle, replacing shell scripts with a more thoroghly engineered Developer Experience.
+
+```sh
+workspace
+│
+└───moon-base          # project
+│   │───actions        # golang actions
+│   │   │   go.mod     # shuttle run build script file as golang code
+│   │   │   build.go
+│   │   shuttle.yaml   # project specific shuttle.yaml file
+│   │   main.go
+│
+└───station-plan       # plan to be shared by projects
+│   │───actions        # golang plan actions
+│   │   │   go.mod     
+│   │   │   build.go
+    │   plan.yaml
+    │   Dockerfile
+```
+
+see [golang actions](./docs/features/golang-actions.md)
+
 ### Telemetry
 
 see [telemetry](./docs/features/telemetry.md)

docs/features/golang-actions.md

@@ -0,0 +1,100 @@
+# Golang Actions
+
+Shuttle supports multiple types of actions. Actions are the things command you
+do on the command line via. shuttle which does stuff.
+
+That is `shuttle run build`, `shuttle run test` etc.
+
+These actions can be defined in multiple ways, and in multiple formats. As the
+`examples` show they can be `docker`, `shell` or `golang`.
+
+As defined in either the `shuttle.yaml` or `plan.yaml` when building a plan.
+
+A script section can be defined.
+
+```yaml
+scripts:
+  build:
+	  actions:
+		  - shell: echo "build...
+```
+
+That of course is a shell action, it can also call a file via:
+`- shell: $scripts/build.sh`
+
+However, we can also use golang. To use golang you need a few prerequisites:
+
+- golang 1.19+
+- or docker
+
+To create an action in your plan, you don't need either the `plan.yaml` or the
+`shuttle.yaml` script sections. You just create a folder:
+`mkdir -p actions && cd actions`
+
+The actions folder is the place our golang code actions will live. Each regular
+golang file in this folder will be treated as an action, this doesn't include
+tests or folders. As such if you need files that aren't actions, create a folder
+and put the code in there.
+
+```bash
+go mod init actions
+go get github.com/lunarway/shuttle
+```
+
+Create a golang submodule, and add shuttle to it.
+
+```bash
+echo <--GOEOF
+package main
+
+import (
+	"context",
+	_ "github.com/lunarway/shuttle" // default the base shuttle so that it doesn't disappear from go.mod
+)
+
+func Build(ctx context.Context) error {
+	println("build")
+
+	return nil
+}
+GOEOF > build.go
+```
+
+This will create a file and a function with the same name. Note, the file name
+and the function name have to match. golang file names support snake_case, and
+golang func names support PascalCase. As such they have to match. Otherwise the
+build will fail.
+
+1. file: "build_production.go" -> func BuildProduction
+2. file: "build.go" -> func Build
+
+Lower case functions are ignored, only 1 public function is allowed pr actions
+file.
+
+1. func handleBuild -> ignored
+2. func Build -> allowed
+3. func build, func Build -> allowed
+4. func Build, func TestBuild -> error (only 1 public function pr file is
+   allowed)
+
+Now you can run the command via. shuttle.
+
+```
+shuttle run build
+stdout: build
+```
+
+## Why
+
+Why would you want such a feature?
+
+- First of all software engineering. Using golang over bash, enables a few
+  things.
+- It is easier to build solid tools in golang than bash. Golang code can be
+  shared and distributed.
+- You can include packages, snippets and whatnot in golang.
+- Golang can more easily be tested and benchmarked.
+- Binaries can be saved and reused to improve performance and startup time.
+- A more thorough user experience can be designed.
+- No longer bound to what is installed on a client machine, you don't need curl,
+  wget, uname, grep, yq, jq etc. installed