ci: add go 1.13.x

* circleci: export GO111MODULE=on, add 1.13.x, remove 1.11.x
* travis: add go 1.13.x

.circleci/config.yml

@@ -8,6 +8,7 @@ references:
     run:
       name: "All Commands"
       command: |
+        export GO111MODULE=on
         mkdir -p bin
         curl -Lso bin/shellcheck https://github.com/caarlos0/shellcheck-docker/releases/download/v0.4.6/shellcheck
         chmod +x bin/shellcheck
@@ -21,7 +22,7 @@ references:
 jobs:
   go-current:
     docker:
-      - image: circleci/golang:1.12
+      - image: circleci/golang:1.13
     working_directory: *workspace
     steps:
       - checkout
@@ -31,7 +32,7 @@ jobs:
           command: diff -u <(echo -n) <(gofmt -d -s .)
   go-previous:
     docker:
-      - image: circleci/golang:1.11
+      - image: circleci/golang:1.12
     working_directory: *workspace
     steps:
       - checkout

.travis.yml

@@ -6,6 +6,7 @@ stages:
 
 go:
   - 1.12.x
+  - 1.13.x
   - tip
 
 env: GO111MODULE=on
@@ -19,6 +20,6 @@ matrix:
     - go: tip
   include:
     - stage: lint
-      go: 1.12.x
+      go: 1.13.x
       before_install: curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b $(go env GOPATH)/bin latest
       script: golangci-lint run -v