Fix deprecated virtual runner and golangci-lint deprecated checkers (#7716)

.github/workflows/fleetctl-preview.yml

@@ -16,7 +16,7 @@ jobs:
     strategy:
       matrix:
         # Doesn't work on Windows because Linux Docker containers are not supported.
-        os: [ubuntu-20.04, ubuntu-18.04, macos-11, macos-12]
+        os: [ubuntu-20.04, ubuntu-22.04, macos-11, macos-12]
     runs-on: ${{ matrix.os }}
     steps:
 

.golangci.yml

@@ -1,7 +1,6 @@
 linters:
   disable-all: true
   enable:
-    - deadcode
     - depguard
     - gosec
     - gocritic
@@ -11,7 +10,6 @@ linters:
     - revive
     - rowserrcheck
     - sqlclosecheck
-    - structcheck
     - typecheck
     - unconvert
     - unused

tools/file-server/main.go

@@ -8,6 +8,7 @@ import (
 func main() {
 	fs := http.FileServer(http.FS(os.DirFS(os.Args[2])))
 	http.Handle("/", fs)
+	//nolint:gosec // G114: file server used for testing purposes only.
 	err := http.ListenAndServe(":"+os.Args[1], nil)
 	if err != nil {
 		panic(err)