test(transport/file): goleak-track Conn.Close

`transport/file/main_test.go` runs `goleak.VerifyTestMain`, so a
leaked server goroutine eventually fails the package — but at
teardown, with no signal pointing to the test that produced the
leak. Mirror `transport/ssh`'s `TestConn_Close_Idempotent` shape:
open a real Conn, call `Close` twice, and wrap the body in
`goleak.VerifyNone(t)` so the failure mode is per-test.

The Conn is constructed against a real on-disk fixture so the
goroutine reaches its real shutdown path
(`cancel → pipe close → <-c.done`); a struct-literal Conn would
short-circuit before that path runs.

The test is not marked `t.Parallel()`: `goleak.VerifyNone`
snapshots the live goroutine set, so concurrent `testing.tRunner`
frames from sibling parallel tests register as unexpected stacks
and fail the verification. The package-wide `VerifyTestMain`
already covers cross-test leak surfaces; this test pins the
per-test shutdown contract.

Signed-off-by: Hidde Beydals <hidde@hhh.computer>

Author: hiddeco

transport/file/conn_test.go

@@ -0,0 +1,43 @@
+package filet
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"go.uber.org/goleak"
+
+	"github.com/hiddeco/go-ls-remote/transport"
+)
+
+// TestConn_Close_NoGoroutineLeaks pins the goroutine-shutdown
+// contract for [Conn.Close]: the single server goroutine that
+// [Transport.Open] spawns must exit before the second [Conn.Close]
+// returns. Wrapping the call sequence in `goleak.VerifyNone` turns
+// a leaked server goroutine into a per-test failure; the
+// package-wide `goleak.VerifyTestMain` only catches the leak at
+// teardown, which obscures the failing call site.
+//
+// The [transport.Conn] is constructed via the same fixture helpers
+// the rest of the package uses so the goroutine reaches its real
+// shutdown path (cancel → pipe-close → `<-c.done`), not a
+// short-circuit on an uninitialised struct.
+//
+//nolint:paralleltest // goleak.VerifyNone snapshots live goroutines; parallel siblings register as unexpected stacks.
+func TestConn_Close_NoGoroutineLeaks(t *testing.T) {
+	defer goleak.VerifyNone(t)
+
+	gitdir := materializeServeableFixture(t, "empty")
+	u, err := transport.ParseURL("file://" + gitdir)
+	require.NoError(t, err)
+
+	tr := New()
+	conn, err := tr.Open(t.Context(), u, transport.OpenOptions{
+		UserAgent: "close-leak-test/0.0",
+	})
+	require.NoError(t, err)
+
+	require.NoError(t, conn.Close(),
+		"first Close returns nil on a clean shutdown")
+	require.NoError(t, conn.Close(),
+		"second Close is a no-op returning nil; goleak verifies the goroutine left")
+}