circleCI yarn cache

config.yml

  steps:
      - checkout
      - restore_cache:
          keys:
            # Find a cache corresponding to this specific yarn.lock checksum
            # when this file is changed, this key will fail
            - v1-yarn-deps-{{ .Branch }}-{{ checksum "yarn.lock" }}
      - run:
          name: install-yarn
          command: npm install -g yarn@v0.24.5
      - run:
          name: yarn-install
          command: yarn
      - save_cache:
          key: v1-yarn-deps-{{ .Branch }}-{{ checksum "yarn.lock" }}
          paths:
            - node_modules