chore(lint): add new linters and update codebase

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

internal/openvpn/extract/extract_test.go

@@ -65,7 +65,6 @@ func Test_extractDataFromLines(t *testing.T) {
 	}
 
 	for name, testCase := range testCases {
-		testCase := testCase
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
 
@@ -129,7 +128,6 @@ func Test_extractDataFromLine(t *testing.T) {
 	}
 
 	for name, testCase := range testCases {
-		testCase := testCase
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
 
@@ -175,7 +173,6 @@ func Test_extractProto(t *testing.T) {
 	}
 
 	for name, testCase := range testCases {
-		testCase := testCase
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
 
@@ -253,7 +250,6 @@ func Test_extractRemote(t *testing.T) {
 	}
 
 	for name, testCase := range testCases {
-		testCase := testCase
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()