all: use Go 1.11.1 in CI

The latest release of Go, 1.11.1 was just published earlier today (on 2
October, 2018).

In the spirit of staying up-to-date with the latest version of Go (see
[1]), let's make sure that we continue to build correctly, even with the
very latest version.

[1] moved the tip to Go 1.11, so there shouldn't be anything surprising
here.

[1]: 074a2d4 (all: use Go 1.11 in CI, 2018-08-28)

.travis.yml

@@ -1,7 +1,7 @@
# http://docs.travis-ci.com/user/languages/go/
language: go

go: 1.11
go: 1.11.1

os:
  - linux

appveyor.yml

@@ -14,8 +14,8 @@ install:
  - rd C:\Go /s /q
  - rd C:\Perl /s /q
  - refreshenv
  - curl -sL -o go1.11.windows-amd64.zip https://storage.googleapis.com/golang/go1.11.windows-amd64.zip
  - 7z x go1.11.windows-amd64.zip -oC:\ >nul
  - curl -sL -o go1.11.1.windows-amd64.zip https://storage.googleapis.com/golang/go1.11.1.windows-amd64.zip
  - 7z x go1.11.1.windows-amd64.zip -oC:\ >nul
  - C:\go\bin\go version
  - cd %USERPROFILE%\src
  - C:\go\bin\go get github.com/josephspurrier/goversioninfo/cmd/goversioninfo