test: use t.Context() instead of context.Background() (#1306)

The test context is cancelled when the test ends, so anything still holding it stops instead of leaking into the next test. Uses inside `t.Cleanup`, `defer` and `go func` blocks are left alone, as the context is already cancelled there.

Stacked on https://gitea.com/gitea/runner/pulls/1305.

Assisted-by: Codet
Co-authored-by: bircni <[email protected]>
Reviewed-on: https://gitea.com/gitea/runner/pulls/1306
Reviewed-by: bircni <[email protected]>

act/container/helpers_test.go

@@ -4,7 +4,6 @@
 package container
 
 import (
-	"context"
 	"testing"
 
 	mobyclient "github.com/moby/moby/client"
@@ -15,7 +14,7 @@ import (
 // so the daemon has to be pinged explicitly here to decide whether to skip.
 func requireDocker(t *testing.T) {
 	t.Helper()
-	ctx := context.Background()
+	ctx := t.Context()
 	cli, err := GetDockerClient(ctx)
 	if err != nil {
 		t.Skipf("skipping: docker client unavailable: %v", err)