update CI to go1.13

.circleci/config.yml

@@ -2,7 +2,7 @@ version: 2
 jobs:
   deps:
     docker:
-      - image: circleci/golang:1.12
+      - image: circleci/golang:1.13
     environment:
       GOPATH: /home/circleci/.go_workspace
     working_directory: /home/circleci/.go_workspace/src/github.com/loadimpact/k6
@@ -22,7 +22,7 @@ jobs:
 
   test:
     docker:
-      - image: circleci/golang:1.12
+      - image: circleci/golang:1.13
     environment:
       GOPATH: /home/circleci/.go_workspace
     working_directory: /home/circleci/.go_workspace/src/github.com/loadimpact/k6
@@ -45,7 +45,7 @@ jobs:
 
   test-prev-golang:
     docker:
-      - image: circleci/golang:1.11
+      - image: circleci/golang:1.12
     environment:
       GOPATH: /home/circleci/.go_workspace
     working_directory: /home/circleci/.go_workspace/src/github.com/loadimpact/k6
@@ -61,7 +61,7 @@ jobs:
 
   build-docker-images:
     docker:
-      - image: circleci/golang:1.12
+      - image: circleci/golang:1.13
     environment:
       GOPATH: /home/circleci/.go_workspace
     working_directory: /home/circleci/.go_workspace/src/github.com/loadimpact/k6
@@ -105,7 +105,7 @@ jobs:
 
   build-linux-packages:
     docker:
-      - image: circleci/golang:1.12
+      - image: circleci/golang:1.13
     environment:
       GOPATH: /home/circleci/.go_workspace
     working_directory: /home/circleci/.go_workspace/src/github.com/loadimpact/k6

appveyor.yml

@@ -10,7 +10,7 @@ environment:
   # specific to go
   VERSION: "%APPVEYOR_REPO_TAG_NAME:v=%"
   GOPATH: c:\gopath
-  GOVERSION: 1.12.1
+  GOVERSION: 1.13
   GOMAXPROCS: 2
   CGO_ENABLED: '0'
   GOARCH: amd64