Add CI cache

.drone.yml

@@ -14,6 +14,26 @@ trigger:
     - push
 
 steps:
+  - name: compute cache key
+    image: docker.io/library/elixir:1.18.3-otp-27
+    commands:
+      - mix_lock_hash=$(sha256sum mix.lock | cut -d ' ' -f 1)
+      - echo "$DRONE_REPO_OWNER/$DRONE_REPO_NAME/$mix_lock_hash" >> .cache_key
+      # Print cache key for debugging
+      - cat .cache_key
+
+  - name: restore-cache
+    image: drillster/drone-volume-cache
+    settings:
+      restore: true
+      mount:
+        - ./deps
+        - ./_build
+      ttl: 30
+    volumes:
+      - name: cache
+        path: /cache
+
   - name: lint
     image: docker.io/library/elixir:1.18.3-otp-27
     commands:
@@ -64,6 +84,22 @@ steps:
       # Run tests
       - mix test
 
+  - name: rebuild-cache
+    image: drillster/drone-volume-cache
+    settings:
+      rebuild: true
+      mount:
+        - ./deps
+        - ./_build
+    volumes:
+      - name: cache
+        path: /cache
+
+volumes:
+  - name: cache
+    host:
+      path: /tmp/drone_cache
+
 ---
 kind: pipeline
 type: docker