diff --git a/vendor/go.etcd.io/etcd/clientv3/credentials/credentials.go b/vendor/go.etcd.io/etcd/clientv3/credentials/credentials.go
new file mode 100644
index 0000000..e6fd75c
--- /dev/null
+++ b/vendor/go.etcd.io/etcd/clientv3/credentials/credentials.go
@@ -0,0 +1,155 @@
+// Copyright 2019 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package credentials implements gRPC credential interface with etcd specific logic.
+// e.g., client handshake with custom authority parameter
+package credentials
+
+import (
+	"context"
+	"crypto/tls"
+	"net"
+	"sync"
+
+	"go.etcd.io/etcd/etcdserver/api/v3rpc/rpctypes"
+	grpccredentials "google.golang.org/grpc/credentials"
+)
+
+// Config defines gRPC credential configuration.
+type Config struct {
+	TLSConfig *tls.Config
+}
+
+// Bundle defines gRPC credential interface.
+type Bundle interface {
+	grpccredentials.Bundle
+	UpdateAuthToken(token string)
+}
+
+// NewBundle constructs a new gRPC credential bundle.
+func NewBundle(cfg Config) Bundle {
+	return &bundle{
+		tc: newTransportCredential(cfg.TLSConfig),
+		rc: newPerRPCCredential(),
+	}
+}
+
+// bundle implements "grpccredentials.Bundle" interface.
+type bundle struct {
+	tc *transportCredential
+	rc *perRPCCredential
+}
+
+func (b *bundle) TransportCredentials() grpccredentials.TransportCredentials {
+	return b.tc
+}
+
+func (b *bundle) PerRPCCredentials() grpccredentials.PerRPCCredentials {
+	return b.rc
+}
+
+func (b *bundle) NewWithMode(mode string) (grpccredentials.Bundle, error) {
+	// no-op
+	return nil, nil
+}
+
+// transportCredential implements "grpccredentials.TransportCredentials" interface.
+type transportCredential struct {
+	gtc grpccredentials.TransportCredentials
+}
+
+func newTransportCredential(cfg *tls.Config) *transportCredential {
+	return &transportCredential{
+		gtc: grpccredentials.NewTLS(cfg),
+	}
+}
+
+func (tc *transportCredential) ClientHandshake(ctx context.Context, authority string, rawConn net.Conn) (net.Conn, grpccredentials.AuthInfo, error) {
+	// Only overwrite when authority is an IP address!
+	// Let's say, a server runs SRV records on "etcd.local" that resolves
+	// to "m1.etcd.local", and its SAN field also includes "m1.etcd.local".
+	// But what if SAN does not include its resolved IP address (e.g. 127.0.0.1)?
+	// Then, the server should only authenticate using its DNS hostname "m1.etcd.local",
+	// instead of overwriting it with its IP address.
+	// And we do not overwrite "localhost" either. Only overwrite IP addresses!
+	if isIP(authority) {
+		target := rawConn.RemoteAddr().String()
+		if authority != target {
+			// When user dials with "grpc.WithDialer", "grpc.DialContext" "cc.parsedTarget"
+			// update only happens once. This is problematic, because when TLS is enabled,
+			// retries happen through "grpc.WithDialer" with static "cc.parsedTarget" from
+			// the initial dial call.
+			// If the server authenticates by IP addresses, we want to set a new endpoint as
+			// a new authority. Otherwise
+			// "transport: authentication handshake failed: x509: certificate is valid for 127.0.0.1, 192.168.121.180, not 192.168.223.156"
+			// when the new dial target is "192.168.121.180" whose certificate host name is also "192.168.121.180"
+			// but client tries to authenticate with previously set "cc.parsedTarget" field "192.168.223.156"
+			authority = target
+		}
+	}
+	return tc.gtc.ClientHandshake(ctx, authority, rawConn)
+}
+
+// return true if given string is an IP.
+func isIP(ep string) bool {
+	return net.ParseIP(ep) != nil
+}
+
+func (tc *transportCredential) ServerHandshake(rawConn net.Conn) (net.Conn, grpccredentials.AuthInfo, error) {
+	return tc.gtc.ServerHandshake(rawConn)
+}
+
+func (tc *transportCredential) Info() grpccredentials.ProtocolInfo {
+	return tc.gtc.Info()
+}
+
+func (tc *transportCredential) Clone() grpccredentials.TransportCredentials {
+	return &transportCredential{
+		gtc: tc.gtc.Clone(),
+	}
+}
+
+func (tc *transportCredential) OverrideServerName(serverNameOverride string) error {
+	return tc.gtc.OverrideServerName(serverNameOverride)
+}
+
+// perRPCCredential implements "grpccredentials.PerRPCCredentials" interface.
+type perRPCCredential struct {
+	authToken   string
+	authTokenMu sync.RWMutex
+}
+
+func newPerRPCCredential() *perRPCCredential { return &perRPCCredential{} }
+
+func (rc *perRPCCredential) RequireTransportSecurity() bool { return false }
+
+func (rc *perRPCCredential) GetRequestMetadata(ctx context.Context, s ...string) (map[string]string, error) {
+	rc.authTokenMu.RLock()
+	authToken := rc.authToken
+	rc.authTokenMu.RUnlock()
+	return map[string]string{rpctypes.TokenFieldNameGRPC: authToken}, nil
+}
+
+func (b *bundle) UpdateAuthToken(token string) {
+	if b.rc == nil {
+		return
+	}
+	b.rc.UpdateAuthToken(token)
+}
+
+func (rc *perRPCCredential) UpdateAuthToken(token string) {
+	rc.authTokenMu.Lock()
+	rc.authToken = token
+	rc.authTokenMu.Unlock()
+}