testutil/integration: fix nightly test behavior (#3343)

Instead of passing errors around with channels, which in this specific test might alter timings, just panic when error is not of "context canceled" kind, during the induced restart phase.

Not ideal, but simple and effective.

category: bug 
ticket: none

testutil/integration/nightly_dkg_test.go

@@ -9,6 +9,7 @@ import (
 	"math/rand"
 	"os"
 	"path"
+	"strings"
 	"testing"
 	"time"
 
@@ -25,8 +26,6 @@ import (
 	"github.com/obolnetwork/charon/p2p"
 )
 
-const ctxCanceledErr = "context canceled"
-
 var (
 	nightly  = flag.Bool("nightly", false, "Enable nightly integration tests")
 	quickRun = flag.Bool("quick-run", false, "Enable quick long-wait DKG that finishes in a minute")
@@ -162,17 +161,16 @@ func mimicDKGNode(parentCtx context.Context, t *testing.T, dkgConf dkg.Config, w
 
 		log.Debug(ctx, "Starting DKG node", z.Int("node", nodeIdx), z.Bool("first_time", firstTime))
 
-		errCh := make(chan error, 1)
 		go func(ctx context.Context) {
 			// Ensure DKGs don't save their artifacts in the same node directory since the current DKG would error
 			// as it would find an existing private key lock file previously created by earlier DKGs.
 			conf := dkgConf
 			conf.DataDir = t.TempDir()
 			err := dkg.Run(ctx, conf)
-			errCh <- err
+			if !strings.Contains(err.Error(), context.Canceled.Error()) {
+				panic("error is not of context canceled kind")
+			}
 		}(ctx)
-		err := <-errCh
-		require.ErrorContains(t, err, ctxCanceledErr)
 
 		return cancelFunc
 	}