ci: Cache Go Dependencies

.drone.yml

@@ -3,13 +3,28 @@ name: Build
 steps:
 - name: Build
   image: golang:1.12
+  volumes:
+  - name: deps
+    path: /go
   commands:
   - go build .
+
 - name: Unit Tests
   image: golang:1.12
+  volumes:
+  - name: deps
+    path: /go
   commands:
   - go test -tag=unit .
+
 - name: Integration Tests
   image: golang:1.12
+  volumes:
+  - name: deps
+    path: /go
   commands:
   - go test -tag=integration .
+
+volumes:
+- name: deps
+  temp: {}