docs: add simple Go guide

Signed-off-by: Tanguy ⧓ Herrmann <tanguy@dagger.io>

docs/plans/go-ci/plan.cue

@@ -0,0 +1,24 @@
+package main
+
+import (
+	"dagger.io/dagger"
+
+	"universe.dagger.io/go"
+	//"universe.dagger.io/bash"
+)
+
+dagger.#Plan & {
+	client: filesystem: "./hello": read: contents: dagger.#FS
+
+	actions: {
+		test: go.#Test & {
+			source:  client.filesystem."./hello".read.contents
+			package: "./..."
+		}
+
+		build: go.#Build & {
+			source: client.filesystem."./hello".read.contents
+		}
+	}
+
+}