[FIXED] assignment copies lock value for crypto/tls.Config

Running `go vet ./...` with `go 1.7.3` would report the following:

```
server/route.go:342: assignment copies lock value to tlsConfig: crypto/tls.Config contains sync.Once contains sync.Mutex
server/server.go:479: assignment copies lock value to config: crypto/tls.Config contains sync.Once contains sync.Mutex
```

Add a “clone” function while waiting for this to be addressed
by the language itself (https://go-review.googlesource.com/#/c/28075/)

.travis.yml

@@ -1,7 +1,7 @@
 language: go
 go:
-- 1.5.4
 - 1.6.3
+- 1.7.3
 env:
   global:
     - GO15VENDOREXPERIMENT=1
@@ -16,5 +16,5 @@ script:
 - go test -i -race ./...
 - go test -v -race ./...
 after_script:
-- if [ "$TRAVIS_GO_VERSION" = "1.6.3" ]; then ./scripts/cov.sh TRAVIS; fi
-- if [ "$TRAVIS_GO_VERSION" = "1.6.3" ] && [ "$TRAVIS_TAG" != "" ]; then ./scripts/cross_compile.sh $TRAVIS_TAG; ghr --username nats-io --token $GITHUB_TOKEN --replace $TRAVIS_TAG pkg/; fi
+- if [ "$TRAVIS_GO_VERSION" = "1.7.3" ]; then ./scripts/cov.sh TRAVIS; fi
+- if [ "$TRAVIS_GO_VERSION" = "1.7.3" ] && [ "$TRAVIS_TAG" != "" ]; then ./scripts/cross_compile.sh $TRAVIS_TAG; ghr --username nats-io --token $GITHUB_TOKEN --replace $TRAVIS_TAG pkg/; fi

server/route.go

@@ -15,6 +15,8 @@ import (
 	"strings"
 	"sync/atomic"
 	"time"
+
+	"github.com/nats-io/gnatsd/util"
 )
 
 // RouteType designates the router type
@@ -339,7 +341,7 @@ func (s *Server) createRoute(conn net.Conn, rURL *url.URL) *client {
 	// Check for TLS
 	if tlsRequired {
 		// Copy off the config to add in ServerName if we
-		tlsConfig := *s.opts.ClusterTLSConfig
+		tlsConfig := util.CloneTLSConfig(s.opts.ClusterTLSConfig)
 
 		// If we solicited, we will act like the client, otherwise the server.
 		if didSolicit {
@@ -347,10 +349,10 @@ func (s *Server) createRoute(conn net.Conn, rURL *url.URL) *client {
 			// Specify the ServerName we are expecting.
 			host, _, _ := net.SplitHostPort(rURL.Host)
 			tlsConfig.ServerName = host
-			c.nc = tls.Client(c.nc, &tlsConfig)
+			c.nc = tls.Client(c.nc, tlsConfig)
 		} else {
 			c.Debugf("Starting TLS route server handshake")
-			c.nc = tls.Server(c.nc, &tlsConfig)
+			c.nc = tls.Server(c.nc, tlsConfig)
 		}
 
 		conn := c.nc.(*tls.Conn)

server/server.go

@@ -18,6 +18,7 @@ import (
 	"time"
 
 	// Allow dynamic profiling.
+	"github.com/nats-io/gnatsd/util"
 	_ "net/http/pprof"
 )
 
@@ -476,9 +477,9 @@ func (s *Server) startMonitoring(secure bool) {
 	if secure {
 		hp = net.JoinHostPort(s.opts.HTTPHost, strconv.Itoa(s.opts.HTTPSPort))
 		Noticef("Starting https monitor on %s", hp)
-		config := *s.opts.TLSConfig
+		config := util.CloneTLSConfig(s.opts.TLSConfig)
 		config.ClientAuth = tls.NoClientCert
-		s.http, err = tls.Listen("tcp", hp, &config)
+		s.http, err = tls.Listen("tcp", hp, config)
 
 	} else {
 		hp = net.JoinHostPort(s.opts.HTTPHost, strconv.Itoa(s.opts.HTTPPort))

util/tls.go

@@ -0,0 +1,46 @@
+// Copyright 2016 Apcera Inc. All rights reserved.
+
+package util
+
+import (
+	"crypto/tls"
+	"reflect"
+)
+
+// CloneTLSConfig returns a copy of c. Only the exported fields are copied.
+// This is temporary, until this is provided by the language.
+// https://go-review.googlesource.com/#/c/28075/
+func CloneTLSConfig(c *tls.Config) *tls.Config {
+	newConfig := &tls.Config{
+		Rand:                     c.Rand,
+		Time:                     c.Time,
+		Certificates:             c.Certificates,
+		NameToCertificate:        c.NameToCertificate,
+		GetCertificate:           c.GetCertificate,
+		RootCAs:                  c.RootCAs,
+		NextProtos:               c.NextProtos,
+		ServerName:               c.ServerName,
+		ClientAuth:               c.ClientAuth,
+		ClientCAs:                c.ClientCAs,
+		InsecureSkipVerify:       c.InsecureSkipVerify,
+		CipherSuites:             c.CipherSuites,
+		PreferServerCipherSuites: c.PreferServerCipherSuites,
+		SessionTicketsDisabled:   c.SessionTicketsDisabled,
+		SessionTicketKey:         c.SessionTicketKey,
+		ClientSessionCache:       c.ClientSessionCache,
+		MinVersion:               c.MinVersion,
+		MaxVersion:               c.MaxVersion,
+		CurvePreferences:         c.CurvePreferences,
+	}
+	fieldName := "DynamicRecordSizingDisabled"
+	if cField := reflect.ValueOf(c).Elem().FieldByName(fieldName); cField.IsValid() {
+		newField := reflect.ValueOf(newConfig).Elem().FieldByName(fieldName)
+		newField.SetBool(cField.Bool())
+
+		fieldName = "Renegotiation"
+		cField = reflect.ValueOf(c).Elem().FieldByName(fieldName)
+		newField = reflect.ValueOf(newConfig).Elem().FieldByName(fieldName)
+		newField.SetInt(cField.Int())
+	}
+	return newConfig
+}