Switch to go modules

appveyor.yml

@@ -2,19 +2,27 @@ version: "{build}"
 
 os: Visual Studio 2017
 build: off
-stack: go 1.10
+stack: go 1.13
 
 environment:
   GOPATH: c:\gopath
+  GO111MODULE: on
 
 clone_folder: c:\gopath\src\github.com\martinlindhe\wmi_exporter
 
 install:
+  - mkdir %GOPATH%\bin
   - set PATH=%GOPATH%\bin;%PATH%
   - set PATH=%PATH%;C:\mingw-w64\x86_64-7.2.0-posix-seh-rt_v5-rev1\mingw64\bin
-  - go get -u github.com/prometheus/promu
-  - go get -u github.com/alecthomas/gometalinter && gometalinter --install
   - choco install gitversion.portable make -y
+  - ps: |
+      appveyor DownloadFile https://github.com/golangci/golangci-lint/releases/download/v1.21.0/golangci-lint-1.21.0-windows-amd64.zip
+      Expand-Archive golangci-lint-1.21.0-windows-amd64.zip
+      Move-Item golangci-lint-1.21.0-windows-amd64\golangci-lint-1.21.0-windows-amd64\golangci-lint.exe $env:GOPATH\bin\golangci-lint.exe
+  - ps: |
+      $env:GO111MODULE="off"
+      go get -u github.com/prometheus/promu
+      $env:GO111MODULE="on"
 
 test_script:
   - make test
@@ -24,6 +32,10 @@ after_test:
 
 build_script:
   - ps: |
+      # go mod download (or, if we don't call it, go build) will write every dependent package name to
+      # stderr, which will be interpreted as an error and abort the build if ErrorActionPreference is Stop,
+      # so we need to run it before setting the preference.
+      go mod download
       $ErrorActionPreference = "Stop"
       gitversion /output json /showvariable FullSemVer | Set-Content VERSION -PassThru
       $Version = Get-Content VERSION