multiple arch CI build

.drone.yml

@@ -3,15 +3,17 @@ kind: pipeline
 name: unit
 
 steps:
-- name: build
-  image: golang
+  # -------------------- tests (host arch only) --------------------
+  - name: test
+    image: golang:1.22-alpine
     pull: if-not-exists
     commands:
-  - go test
-  - go build
+      - go test ./...
 
+  # -------------------- build + push multi-arch image --------------------
   - name: publish
     image: plugins/docker:latest
+    privileged: true         # needed for docker/buildx 
     settings:
       username:
         from_secret: docker-user
@@ -19,3 +21,19 @@ steps:
         from_secret: docker-pw
       repo:
         from_secret: docker-repo
+
+      # build context & dockerfile
+      context: .
+      dockerfile: Dockerfile
+
+      # enable buildx / multi-arch
+      buildx: true
+      platforms:
+        - linux/amd64
+        - linux/arm64
+        - linux/arm/v7
+
+      # tags to push (all as a single multi-arch manifest)
+      tags:
+        - latest
+