fix parsing go1.23 stack traces

fixes #90

Author: stapelberg

stack/context.go

@@ -270,7 +270,7 @@ var (
 // These are effectively constants.
 var (
 	// gotRoutineHeader
-	reRoutineHeader = regexp.MustCompile("^([ \t]*)goroutine (\\d+) \\[([^\\]]+)\\]\\:$")
+	reRoutineHeader = regexp.MustCompile("^([ \t]*)goroutine (\\d+)(?: gp=[^ ]+ m=[^ ]+(?: mp=[^ ]+)?)? \\[([^\\]]+)\\]\\:$")
 	reMinutes       = regexp.MustCompile(`^(\d+) minutes$`)
 
 	// gotUnavail

stack/context_test.go

@@ -1348,6 +1348,9 @@ func TestScanSnapshotSyntheticTwoSnapshots(t *testing.T) {
 	prefix := bytes.Buffer{}
 	s, suffix, err := ScanSnapshot(&in, &prefix, defaultOpts())
 	compareErr(t, nil, err)
+	if err != nil {
+		t.Fatal(err)
+	}
 	if !s.guessPaths() {
 		t.Error("expected success")
 	}
@@ -1523,6 +1526,9 @@ func TestGomoduleComplex(t *testing.T) {
 	prefix := bytes.Buffer{}
 	s, suffix, err := ScanSnapshot(bytes.NewReader(out), &prefix, defaultOpts())
 	compareErr(t, io.EOF, err)
+	if err != nil {
+		t.Fatal(err)
+	}
 	if !s.guessPaths() {
 		t.Error("expected success")
 	}