ci: update circle ci to v2 (#3850)

circle.yml

@@ -1,22 +1,12 @@
-machine:
-  environment:
-    GITHUB_PROJECT_USERNAME: pingcap
-    GITHUB_PROJECT_REPONAME: tidb
-    GODIST: "go1.8.1.linux-amd64.tar.gz"
-  post:
-    - mkdir -p download
-    - test -e download/$GODIST || curl -o download/$GODIST https://storage.googleapis.com/golang/$GODIST
-    - sudo rm -rf /usr/local/go
-    - sudo tar -C /usr/local -xzf download/$GODIST
+version: 2
 
-dependencies:
-  cache_directories:
-    - ~/download
-  override:
-    - mkdir -p $HOME/.go_project/src/github.com/$GITHUB_PROJECT_USERNAME
-    - ln -fs $HOME/$CIRCLE_PROJECT_REPONAME $HOME/.go_project/src/github.com/$GITHUB_PROJECT_USERNAME/$GITHUB_PROJECT_REPONAME
-    - echo 'export GOPATH=$GOPATH:$HOME/.go_project' >> ~/.circlerc
-
-test:
-  override:
-    - cd $HOME/.go_project/src/github.com/$GITHUB_PROJECT_USERNAME/$GITHUB_PROJECT_REPONAME && make dev
+jobs:
+  build:
+    docker:
+      - image: golang:1.8.1
+    working_directory: /go/src/github.com/pingcap/tidb
+    steps:
+      - checkout
+      - run:
+          name: "Build & Test"
+          command: make dev