enable drone cache

.drone.yml

@@ -2,8 +2,25 @@
 kind: pipeline
 name: testing
 steps:
+
+- name: restore-cache
+  image: meltwater/drone-cache:dev
+  pull: true
+  settings:
+    backend: "filesystem"
+    restore: true
+    cache_key: "volume"
+    archive_format: "gzip"
+    mount:
+      - '${GOPATH}/pkg/mod'
+  volumes:
+  - name: cache
+    path: /tmp/cache
+
 - name: test-vet
   image: golang:1.11
+  depends_on:
+  - restore-cache
   environment:
     GO111MODULE: "on"
     GOPROXY: "https://goproxy.cn"
@@ -14,8 +31,26 @@ steps:
     - push
     - pull_request
 
+- name: rebuild-cache
+  image: meltwater/drone-cache:dev
+  depends_on:
+  - test-vet
+  pull: true
+  settings:
+    backend: "filesystem"
+    rebuild: true
+    cache_key: "volume"
+    archive_format: "gzip"
+    mount:
+      - '${GOPATH}/pkg/mod'
+  volumes:
+  - name: cache
+    path: /tmp/cache
+
 - name: test-sqlite
   image: golang:1.12
+  depends_on:
+  - rebuild-cache
   environment:
     GO111MODULE: "on"
     GOPROXY: "https://goproxy.cn"
@@ -31,6 +66,8 @@ steps:
 
 - name: test-mysql
   image: golang:1.12
+  depends_on:
+  - rebuild-cache
   environment:
     GO111MODULE: "on"
     GOPROXY: "https://goproxy.cn"
@@ -49,6 +86,8 @@ steps:
 
 - name: test-mysql8
   image: golang:1.12
+  depends_on:
+  - rebuild-cache
   environment:
     GO111MODULE: "on"
     GOPROXY: "https://goproxy.cn"
@@ -68,6 +107,7 @@ steps:
 - name: test-mysql-utf8mb4
   image: golang:1.12
   depends_on:
+  - rebuild-cache
   - test-mysql
   environment:
     GO111MODULE: "on"
@@ -108,6 +148,8 @@ steps:
 - name: test-postgres
   pull: default
   image: golang:1.12
+  depends_on:
+  - rebuild-cache
   environment:
     GO111MODULE: "on"
     GOPROXY: "https://goproxy.cn"
@@ -147,6 +189,8 @@ steps:
 - name: test-mssql
   pull: default
   image: golang:1.12
+  depends_on:
+  - rebuild-cache
   environment:
     GO111MODULE: "on"
     GOPROXY: "https://goproxy.cn"
@@ -165,6 +209,8 @@ steps:
 - name: test-tidb
   pull: default
   image: golang:1.12
+  depends_on:
+  - rebuild-cache
   environment:
     GO111MODULE: "on"
     GOPROXY: "https://goproxy.cn"