run golangci-lint on travis

travis/install.sh

@@ -2,6 +2,11 @@
 
 set -e
 
+# Install golanci 1.21.0
+if [[ "$TRAVIS_GO_VERSION" =~ ^1\.13\. ]]; then
+    curl -sfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh| sh -s -- -b $(go env GOPATH)/bin v1.21.0
+fi
+
 # Only do this for go1.12 when modules are on so that it doesn't need to be done when modules are off as well.
 if [[ "$TRAVIS_GO_VERSION" =~ ^1\.13\. ]] && [[ "$TRAVIS_OS_NAME" == "linux" ]] && [[ "$GO111MODULE" == "on" ]]; then
     GO111MODULE=off go get github.com/dgsb/gox

travis/lint.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+if [[ "$TRAVIS_GO_VERSION" =~ ^1\.13\. ]] && [[ "$TRAVIS_OS_NAME" == "linux" ]] && [[ "$GO111MODULE" == "on" ]]; then
+    $(go env GOPATH)/bin/golangci-lint run ./...
+fi