Improve go use case example according to Gerhard's review

Signed-off-by: Vasek - Tom C <tom.chauveau@epitech.eu>

docs/tests/use-cases/ci-cd-for-go-project/retrieve-go-project/dagger.cue

@@ -0,0 +1,18 @@
+package main
+
+import (
+	"dagger.io/dagger"
+)
+
+dagger.#Plan & {
+	// Retrieve go source code
+	client: filesystem: ".": read: {
+		contents: dagger.#FS
+		include: ["go.mod", "go.sum", "**/*.go"]
+	}
+
+	actions: {
+		// Alias to code directory
+		_code: client.filesystem.".".read.contents
+	}
+}