remove deprecated usage of varcheck, deadcode, and structcheck

.golangci.yml

@@ -3,11 +3,9 @@ run:
 linters:
   disable-all: true
   enable:
-    - deadcode
     - govet
     - ineffassign
     - staticcheck
-    - structcheck
     - typecheck
-    - varcheck
     - whitespace
+    - unused

coremain/run.go

@@ -170,6 +170,7 @@ var (
 
 // Build information obtained with the help of -ldflags
 var (
+	// nolint
 	appVersion = "(untracked dev build)" // inferred at startup
 	devBuild   = true                    // inferred at startup
 

test/presubmit_test.go

@@ -125,7 +125,7 @@ func (l logfmt) Visit(n ast.Node) ast.Visitor {
 	if !ok {
 		return l
 	}
-	if id.Name != "t" { //t *testing.T
+	if id.Name != "t" { // t *testing.T
 		return l
 	}
 
@@ -182,41 +182,6 @@ func TestImportTesting(t *testing.T) {
 	}
 }
 
-type hasImportTestingWalker struct {
-	Errors []error
-}
-
-func (w *hasImportTestingWalker) walk(path string, info os.FileInfo, _ error) error {
-	// only for regular files, not starting with a . and those that are go files.
-	if !info.Mode().IsRegular() {
-		return nil
-	}
-	if strings.HasPrefix(path, "../.") {
-		return nil
-	}
-	if strings.Contains(path, "/vendor") {
-		return nil
-	}
-	if strings.HasSuffix(path, "_test.go") {
-		return nil
-	}
-
-	if strings.HasSuffix(path, ".go") {
-		fs := token.NewFileSet()
-		f, err := parser.ParseFile(fs, path, nil, parser.AllErrors)
-		if err != nil {
-			return err
-		}
-		for _, im := range f.Imports {
-			if im.Path.Value == `"testing"` {
-				absPath, _ := filepath.Abs(path)
-				w.Errors = append(w.Errors, fmt.Errorf("file %q is importing %q", absPath, "testing"))
-			}
-		}
-	}
-	return nil
-}
-
 func TestImportOrdering(t *testing.T) {
 	walker := testImportOrderingWalker{}
 	err := filepath.Walk("..", walker.walk)