proxy: Detect Goroutine leaks via goleak

We have been bitten by Goroutine leaks in the GRPC proxying code in some
cases, but until now we didn't have any meaningful way to detect this
kind of leak.

Fix the test gap by using go.uber.org/goleak to detect any leaked
Goroutines after the test. This nicely demonstrates that we currently do
have a Goroutine leak in the proxying code in `forwardClienToServers()`.

3 files changed, 7 insertions, 6 deletions

diff --git a/go.mod b/go.mod
index cf93bb0fe..ac8a2347b 100644
--- a/go.mod
+++ b/go.mod
@@ -41,6 +41,7 @@ require (
 	github.com/uber/jaeger-client-go v2.15.0+incompatible
 	gitlab.com/gitlab-org/gitlab-shell v1.9.8-0.20201117050822-3f9890ef73dc
 	gitlab.com/gitlab-org/labkit v1.0.0
+	go.uber.org/goleak v1.1.10
 	golang.org/x/exp v0.0.0-20200331195152-e8c3332aa8e5 // indirect
 	golang.org/x/sync v0.0.0-20200625203802-6e8e738ad208
 	golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4
diff --git a/go.sum b/go.sum
index ee105d591..635d61c68 100644
--- a/go.sum
+++ b/go.sum
@@ -430,6 +430,8 @@ go.opencensus.io v0.22.2/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
 go.uber.org/atomic v1.3.2/go.mod h1:gD2HeocX3+yG+ygLZcrzQJaqmWj9AIm7n08wl/qW/PE=
 go.uber.org/atomic v1.4.0 h1:cxzIVoETapQEqDhQu3QfnvXAV4AlzcvUCxkVUFw3+EU=
 go.uber.org/atomic v1.4.0/go.mod h1:gD2HeocX3+yG+ygLZcrzQJaqmWj9AIm7n08wl/qW/PE=
+go.uber.org/goleak v1.1.10 h1:z+mqJhf6ss6BSfSM671tgKyZBFPTTJM+HLxnhPC3wu0=
+go.uber.org/goleak v1.1.10/go.mod h1:8a7PlsEVH3e/a/GLqe5IIrQx6GzcnRmZEufDUTk4A7A=
 go.uber.org/multierr v1.1.0/go.mod h1:wR5kodmAFQ0UK8QlbwjlSNy0Z68gJhDJUG5sjR94q/0=
 go.uber.org/zap v1.10.0/go.mod h1:vwi/ZaCAaUcBkycHslxD9B2zi4UTXhF60s6SWpuDF0Q=
 golang.org/x/crypto v0.0.0-20180904163835-0709b304e793/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
@@ -462,6 +464,7 @@ golang.org/x/lint v0.0.0-20190301231843-5614ed5bae6f/go.mod h1:UVdnD1Gm6xHRNCYTk
 golang.org/x/lint v0.0.0-20190313153728-d0100b6bd8b3/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=
 golang.org/x/lint v0.0.0-20190409202823-959b441ac422/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=
 golang.org/x/lint v0.0.0-20190909230951-414d861bb4ac/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=
+golang.org/x/lint v0.0.0-20190930215403-16217165b5de/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=
 golang.org/x/lint v0.0.0-20191125180803-fdd1cda4f05f h1:J5lckAjkw6qYlOZNj90mLYNTEKDvWeuc1yieZ8qUzUE=
 golang.org/x/lint v0.0.0-20191125180803-fdd1cda4f05f/go.mod h1:5qLYkcX4OjUUV8bRuDixDT3tpyyb+LUpUlRWLxfhWrs=
 golang.org/x/mobile v0.0.0-20190312151609-d3739f865fa6/go.mod h1:z+o9i4GpDbdi3rU15maQ/Ox0txvL9dWGYEHz965HBQE=
@@ -570,6 +573,7 @@ golang.org/x/tools v0.0.0-20190816200558-6889da9d5479/go.mod h1:b+2E5dAYhXwXZwtn
 golang.org/x/tools v0.0.0-20190911174233-4f2ddba30aff/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.0.0-20191004055002-72853e10c5a3/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.0.0-20191012152004-8de300cfc20a/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/tools v0.0.0-20191108193012-7d206e10da11/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.0.0-20191125144606-a911d9008d1f/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.0.0-20191216173652-a0e659d51361/go.mod h1:TB2adYChydJhpapKDTa4BR/hXlZSLoq2Wpct/0txZ28=
 golang.org/x/tools v0.0.0-20200117161641-43d50277825c/go.mod h1:TB2adYChydJhpapKDTa4BR/hXlZSLoq2Wpct/0txZ28=
diff --git a/internal/praefect/grpc-proxy/proxy/handler_test.go b/internal/praefect/grpc-proxy/proxy/handler_test.go
index 545171f19..9d97dfcf4 100644
--- a/internal/praefect/grpc-proxy/proxy/handler_test.go
+++ b/internal/praefect/grpc-proxy/proxy/handler_test.go
@@ -12,7 +12,6 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"net/url"
-	"os"
 	"path/filepath"
 	"strings"
 	"testing"
@@ -31,6 +30,7 @@ import (
 	"gitlab.com/gitlab-org/gitaly/internal/praefect/grpc-proxy/proxy"
 	pb "gitlab.com/gitlab-org/gitaly/internal/praefect/grpc-proxy/testdata"
 	"gitlab.com/gitlab-org/gitaly/internal/testhelper"
+	"go.uber.org/goleak"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/metadata"
@@ -49,15 +49,11 @@ const (
 )
 
 func TestMain(m *testing.M) {
-	os.Exit(testMain(m))
-}
-
-func testMain(m *testing.M) int {
 	defer testhelper.MustHaveNoChildProcess()
 	cleanup := testhelper.Configure()
 	defer cleanup()
 
-	return m.Run()
+	goleak.VerifyTestMain(m)
 }
 
 // asserting service is implemented on the server side and serves as a handler for stuff