build: drop go Dep, switch to modules, support Go 1.13

bump enumer to v1.1.1
bump golangci-lint to v1.17.1

no `go mod tidy` because 1.13 and 1.12 seem to alter each other's output

fixes #112

.circleci/config.yml

@@ -5,6 +5,7 @@ workflows:
     jobs:
       - build-1.11
       - build-1.12
+      - build-1.13
       - build-latest
 jobs:
   # build-latest serves as the template
@@ -27,11 +28,12 @@ jobs:
           command: |
             # used by pip (for docs)
             echo 'export PATH="$HOME/.local/bin:$PATH"' >> $BASH_ENV
+            # we use modules
+            echo 'export GO111MODULE=on' >> $BASH_ENV
 
       - restore_cache:
           keys:
             - source
-            - vendor
             - protobuf
 
       - checkout
@@ -53,12 +55,6 @@ jobs:
       - run: sudo apt install python3 python3-pip libgirepository1.0-dev
       - run: ./lazy.sh devsetup
 
-      - run: make vendordeps
-      - save_cache:
-          key: vendor
-          paths:
-            - "./vendor"
-            
       - run: make
       - run: make vet
       - run: make test
@@ -98,12 +94,17 @@ jobs:
               -X POST \
               -d '{"context":"zrepl/publish-ci-artifacts", "state": "success", "description":"CI Build Artifacts for '"$JOB_NAME"'", "target_url":"https://minio.cschwarz.com/minio/zrepl-ci-artifacts/'"$COMMIT"'/"}'
 
-
   build-1.11:
     <<: *build-latest
     docker:
-      - image: circleci/golang:1.11
+    - image: circleci/golang:1.11
+
   build-1.12:
     <<: *build-latest
     docker:
     - image: circleci/golang:1.12
+
+  build-1.13:
+    <<: *build-latest
+    docker:
+    - image: circleci/golang:1.13