update action to dagger 0.2

- Remove AGE key setup
- Update README to use `dagger do`
- Update tests to dagger 0.2

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

test/cue.mod/pkg/universe.dagger.io/go/container.cue

@@ -0,0 +1,41 @@
+// Go operation
+package go
+
+import (
+	"dagger.io/dagger"
+	"universe.dagger.io/docker"
+)
+
+// A standalone go environment to run go command
+#Container: {
+	// Container app name
+	name: *"go_builder" | string
+
+	// Source code
+	source: dagger.#FS
+
+	// Use go image
+	_image: #Image
+
+	_sourcePath: "/src"
+	_cachePath:  "/root/.cache/gocache"
+
+	docker.#Run & {
+		input:   *_image.output | docker.#Image
+		workdir: "/src"
+		command: name: "go"
+		mounts: {
+			"source": {
+				dest:     _sourcePath
+				contents: source
+			}
+			"go assets cache": {
+				contents: dagger.#CacheDir & {
+					id: "\(name)_assets"
+				}
+				dest: _cachePath
+			}
+		}
+		env: GOMODCACHE: _cachePath
+	}
+}