Merge pull request #126 from digineo/go-1.11

Run tests with Go 1.11

.travis.yml

@@ -2,8 +2,8 @@ language: go
 dist: trusty
 sudo: required
 go:
-  - 1.9.x
   - 1.10.x
+  - 1.11.x
 env:
   - FTP_SERVER=vsftpd
   - FTP_SERVER=proftpd