interfaces: bump appveyor version

Author: rjeczalik

appveyor.yml

@@ -5,9 +5,11 @@ os: Windows Server 2012 R2
 clone_folder: c:\projects\src\github.com\rjeczalik\interfaces
 
 environment:
- PATH: c:\projects\bin;%PATH%
+ PATH: c:\projects\bin;C:\msys64\mingw64\bin;%PATH%
  GOPATH: c:\projects
- GOVERSION: 1.8.3
+ GOVERSION: 1.12.4
+ GOCACHE: c:\gocache
+ GO111MODULE: on
 
 install:
  - rmdir c:\go /s /q
@@ -19,7 +21,6 @@ install:
  - go get -v -t ./...
 
 build_script:
- - go tool vet -all .
  - go install ./...
  - go test -race -v ./...