Add linter to makefile and to circleci

.circleci/config.yml

@@ -8,6 +8,7 @@ jobs:
       - image: circleci/golang:1.13
     steps:
       - checkout
+      - run: curl -sfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh| sh -s -- -b $(go env GOPATH)/bin v1.20.0
       - run: make
       - persist_to_workspace:
           root: .