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/image.cue

@@ -0,0 +1,37 @@
+package go
+
+import (
+	"universe.dagger.io/docker"
+)
+
+// Go image default version
+#DefaultVersion: "1.16"
+
+// Build a go base image
+#Image: {
+	version: *#DefaultVersion | string
+
+	packages: [pkgName=string]: version: string | *""
+
+	// FIXME Basically a copy of alpine.#Build with a different image
+	// Should we create a special definition?
+	docker.#Build & {
+		steps: [
+			docker.#Pull & {
+				source: "index.docker.io/golang:\(version)-alpine"
+			},
+			for pkgName, pkg in packages {
+				docker.#Run & {
+					command: {
+						name: "apk"
+						args: ["add", "\(pkgName)\(pkg.version)"]
+						flags: {
+							"-U":         true
+							"--no-cache": true
+						}
+					}
+				}
+			},
+		]
+	}
+}