test: add TLS mixed soak with paced clients

transport/http2/soak_test.go

@@ -22,14 +22,7 @@ import (
 // verification. Linux acceptance runs set GO_OMNI_HTTP2_SOAK_DURATION=30m.
 func TestTLSSoak(t *testing.T) {
 	started := time.Now()
-	duration := 3 * time.Second
-	if value := os.Getenv("GO_OMNI_HTTP2_SOAK_DURATION"); value != "" {
-		parsed, err := time.ParseDuration(value)
-		if err != nil || parsed <= 0 {
-			t.Fatalf("invalid GO_OMNI_HTTP2_SOAK_DURATION %q: %v", value, err)
-		}
-		duration = parsed
-	}
+	duration := soakDuration(t)
 	logSoakResources(t, started, "before", 0, 0, Stats{})
 
 	certificate, roots := testCertificate(t)
@@ -172,6 +165,18 @@ func TestTLSSoak(t *testing.T) {
 	}
 }
 
+func soakDuration(t *testing.T) time.Duration {
+	t.Helper()
+	if value := os.Getenv("GO_OMNI_HTTP2_SOAK_DURATION"); value != "" {
+		duration, err := time.ParseDuration(value)
+		if err != nil || duration <= 0 {
+			t.Fatalf("invalid GO_OMNI_HTTP2_SOAK_DURATION %q: %v", value, err)
+		}
+		return duration
+	}
+	return 3 * time.Second
+}
+
 // These measurements cover the client and server in the same test process.
 // RSS includes race runtime allocations that do not appear in Go heap stats.
 func logSoakResources(t *testing.T, started time.Time, phase string, requests, failures uint64, stats Stats) {