chore(lint): add forbidigo rules to enforce t.Context() in tests

Add linter rules to prevent usage of context.Background() and
context.TODO() in test files - t.Context() should be used instead.

The rules only apply to *_test.go files, not production code.

Note: os.Setenv is not covered by forbidigo due to a limitation where
it only catches calls when the return value is assigned. However,
errcheck will flag unchecked os.Setenv calls.

Assisted-By: cagent
Signed-off-by: David Gageot <david.gageot@docker.com>

.golangci.yml

@@ -8,6 +8,7 @@ linters:
     - depguard
     - errcheck
     - errorlint
+    - forbidigo
     - gocritic
     - gocyclo
     - gomodguard
@@ -38,6 +39,15 @@ linters:
               desc: use stdlib slices package
             - pkg: gopkg.in/yaml.v2
               desc: compose-go uses yaml.v3
+    forbidigo:
+      analyze-types: true
+      forbid:
+        - pattern: 'context\.Background'
+          pkg: '^context$'
+          msg: "in tests, use t.Context() instead of context.Background()"
+        - pattern: 'context\.TODO'
+          pkg: '^context$'
+          msg: "in tests, use t.Context() instead of context.TODO()"
     gocritic:
       disabled-checks:
         - paramTypeCombine
@@ -74,6 +84,10 @@ linters:
       - third_party$
       - builtin$
       - examples$
+    rules:
+      - path-except: '_test\.go'
+        linters:
+          - forbidigo
 issues:
   max-issues-per-linter: 0
   max-same-issues: 0

pkg/compose/kill_test.go

@@ -127,6 +127,7 @@ func containerLabels(service string, oneOff bool) map[string]string {
 }
 
 func anyCancellableContext() gomock.Matcher {
+	//nolint:forbidigo // This creates a context type for gomock matching, not for actual test usage
 	ctxWithCancel, cancel := context.WithCancel(context.Background())
 	cancel()
 	return gomock.AssignableToTypeOf(ctxWithCancel)