chore(lint): add new linters and update codebase

- add canonicalheader
- add copyloopvar
- add fatcontext
- add intrange

internal/server/middlewares/auth/apikey.go

@@ -27,7 +27,7 @@ func (a *apiKeyMethod) equal(other authorizationChecker) bool {
 }
 
 func (a *apiKeyMethod) isAuthorized(_ http.Header, request *http.Request) bool {
-	xAPIKey := request.Header.Get("X-API-Key")
+	xAPIKey := request.Header.Get("X-API-Key") //nolint:canonicalheader
 	if xAPIKey == "" {
 		xAPIKey = request.URL.Query().Get("api_key")
 	}

internal/server/middlewares/auth/configfile_test.go

@@ -57,7 +57,6 @@ routes = ["GET /v1/vpn/status"]
 	}
 
 	for name, testCase := range testCases {
-		testCase := testCase
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
 

internal/server/middlewares/auth/lookup_test.go

@@ -44,7 +44,6 @@ func Test_settingsToLookupMap(t *testing.T) {
 	}
 
 	for name, testCase := range testCases {
-		testCase := testCase
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
 

internal/server/middlewares/auth/middleware_test.go

@@ -80,7 +80,6 @@ func Test_authHandler_ServeHTTP(t *testing.T) {
 	}
 
 	for name, testCase := range testCases {
-		testCase := testCase
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
 			ctrl := gomock.NewController(t)