use Go modules on CI

.appveyor.yml

@@ -1,8 +1,9 @@
 version: "{build}"
 clone_depth: 1
-clone_folder: c:\gopath\src\github.com\rhysd\go-github-selfupdate
+clone_folder: c:\outside-gopath
 environment:
     GOPATH: c:\gopath
+    GO111MODULE: on
 install:
     - echo %PATH%
     - echo %GOPATH%

.travis.yml

@@ -2,10 +2,12 @@ language: go
 os:
   - linux
   - osx
+env:
+  - GO111MODULE=on
 install:
-  - go get -t -d -v ./...
   - go version
   - go env
+  - go get -t -d -v ./...
 script:
   - go build ./selfupdate/
   - go build ./cmd/selfupdate-example/