Internals: Switch to v2 go.mod, drop GOPATH, and fix Azure Pipelines (#595)

* Switched to v2 go.mod

Also set GO111MODULE=on in build stuff to always use Go modules
even when in GOPATH.

* Ensure go.mod, go.sum, and vendor are up to date

* Attempt to fix Azure pipelines

* Add set -e to properly fail on exit (it didn't seem to be
  propagating properly before).
* Set workingDirectory for GoFmt and GoGen (this might be why it
  fails unlike compile and unitests).

* Another attempt to fix Azure Pipelines

* Use the Go env template for all go-related jobs.

* Completely fixed Azure Pipelines

* Added a display name to GoFmt for consistency.
* Fixed diffs for GoFmt and GoGen.
* Show git status for checks.

* Drop GOPATH for tests

TODO: Do the same for integration tests.

* Drop GOPATH for integration tests

* Show more diffs

* Regenerate provider support matrix

This wasn't done in #590...

build/azure-pipelines/go-env.yaml

@@ -1,12 +1,6 @@
 # shared step for setting up go env
 # see https://docs.microsoft.com/en-us/azure/devops/pipelines/languages/go?view=azure-devops#build-a-container-image
 steps:
-- script: |
-    mkdir -p '$(GOBIN)'
-    mkdir -p '$(GOPATH)/pkg'
-    mkdir -p '$(modulePath)'
-    shopt -s extglob
-    mv !(gopath) '$(modulePath)'
-    echo '##vso[task.prependpath]$(GOBIN)'
-    echo '##vso[task.prependpath]$(GOROOT)/bin'
-  displayName: 'Set up the Go workspace'
+- task: GoTool@0
+  inputs:
+    version: '1.13.6'

build/azure-pipelines/integration.yml

@@ -1,9 +1,5 @@
 variables:
-  GOBIN:  '$(GOPATH)/bin' # Go binaries path
-  GOROOT: '/usr/local/go1.13' # Go installation path
-  GOPATH: '$(system.defaultWorkingDirectory)/gopath' # Go workspace path
-  modulePath: '$(GOPATH)/src/github.com/$(build.repository.name)' # Path to the module's code
-  wd: '$(modulePath)/integrationTest'
+  wd: '$(System.DefaultWorkingDirectory)/integrationTest'
 
 trigger:
   batch: "true"

build/build.go

@@ -17,12 +17,13 @@ var goos = flag.String("os", "", "OS to build (linux, windows, or darwin) Defaul
 func main() {
 	flag.Parse()
 	flags := fmt.Sprintf(`-s -w -X main.SHA="%s" -X main.BuildTime=%d`, getVersion(), time.Now().Unix())
-	pkg := "github.com/StackExchange/dnscontrol"
+	pkg := "github.com/StackExchange/dnscontrol/v2"
 
 	build := func(out, goos string) {
 		log.Printf("Building %s", out)
 		cmd := exec.Command("go", "build", "-o", out, "-ldflags", flags, pkg)
 		os.Setenv("GOOS", goos)
+		os.Setenv("GO111MODULE", "on")
 		cmd.Stderr = os.Stderr
 		cmd.Stdout = os.Stdout
 		err := cmd.Run()

build/generate/featureMatrix.go

@@ -6,8 +6,8 @@ import (
 	"io/ioutil"
 	"sort"
 
-	"github.com/StackExchange/dnscontrol/providers"
-	_ "github.com/StackExchange/dnscontrol/providers/_all"
+	"github.com/StackExchange/dnscontrol/v2/providers"
+	_ "github.com/StackExchange/dnscontrol/v2/providers/_all"
 )
 
 func generateFeatureMatrix() error {