Upgrade linter and travis to go1.13 (#949)

.golangci.yaml

@@ -174,6 +174,7 @@ linters:
     - lll
     - maligned
     - prealloc
+    - wsl
 
 
 # rules to deal with reported isues

.travis.yml

@@ -20,22 +20,22 @@ jobs:
   - stage: lint
     # Run linting in one Go environment only.
     script: ./ci/lint.sh
-    go: 1.12.x
+    go: 1.13.x
     env:
     - GO111MODULE=on
-    - GOLANGCI_VERSION="v1.17.1"
+    - GOLANGCI_VERSION="v1.21.0"
   - stage: test
     # Run tests in a combination of Go environments.
     script: ./ci/test.sh
-    go: 1.11.x
+    go: 1.12.x
     env:
     - GO111MODULE=off
   - script: ./ci/test.sh
-    go: 1.11.x
+    go: 1.12.x
     env:
     - GO111MODULE=on
   - script: ./ci/test.sh
-    go: 1.12.x
+    go: 1.13.x
     env:
     - GO111MODULE=on
     - REPORT_COVERAGE=1

ci/bintray.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 set -u -e -x -o pipefail
 
-go version | grep go1.12 || exit
+go version | grep go1.13 || exit
 
 VERSION=$(git describe --tags)
 mkdir ci/binaries