add a Transport config option for the key used to encrypt tokens (#4066)

* add a Transport config option for the key used to encrypt tokens

* handshake: remove unused error return values

server.go

@@ -2,7 +2,6 @@ package quic
 
 import (
 	"context"
-	"crypto/rand"
 	"crypto/tls"
 	"errors"
 	"fmt"
@@ -227,18 +226,15 @@ func newServer(
 	config *Config,
 	tracer logging.Tracer,
 	onClose func(),
+	tokenGeneratorKey TokenGeneratorKey,
 	disableVersionNegotiation bool,
 	acceptEarly bool,
-) (*baseServer, error) {
-	tokenGenerator, err := handshake.NewTokenGenerator(rand.Reader)
-	if err != nil {
-		return nil, err
-	}
+) *baseServer {
 	s := &baseServer{
 		conn:                      conn,
 		tlsConf:                   tlsConf,
 		config:                    config,
-		tokenGenerator:            tokenGenerator,
+		tokenGenerator:            handshake.NewTokenGenerator(tokenGeneratorKey),
 		connIDGenerator:           connIDGenerator,
 		connHandler:               connHandler,
 		connQueue:                 make(chan quicConn),
@@ -260,7 +256,7 @@ func newServer(
 	go s.run()
 	go s.runSendQueue()
 	s.logger.Debugf("Listening for %s connections on %s", conn.LocalAddr().Network(), conn.LocalAddr().String())
-	return s, nil
+	return s
 }
 
 func (s *baseServer) run() {