install yarn

.circleci/config.yml

@@ -1,4 +1,10 @@
-version: 2.0
+workflows:
+  version: 2.1
+  do-some-magic:
+    jobs:
+      - build
+
+version: 2.1
 jobs:
   build:
     docker:
@@ -8,4 +14,7 @@ jobs:
           password: $PSW_DOCKER  # context / project UI env-var reference
     steps:
       - checkout # check out the code in the project directory
-      - run: echo "hello world" # run the `echo` command
+      - node/with-cache:
+          steps:
+            - run: yarn install
+            - run: npm-v1-dependencies-{{ checksum "yarn.lock" }}