diff --git a/vendor/google.golang.org/grpc/internal/serviceconfig/serviceconfig.go b/vendor/google.golang.org/grpc/internal/serviceconfig/serviceconfig.go
new file mode 100644
index 0000000..badbdbf
--- /dev/null
+++ b/vendor/google.golang.org/grpc/internal/serviceconfig/serviceconfig.go
@@ -0,0 +1,180 @@
+/*
+ *
+ * Copyright 2020 gRPC 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 serviceconfig contains utility functions to parse service config.
+package serviceconfig
+
+import (
+	"encoding/json"
+	"fmt"
+	"time"
+
+	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/grpclog"
+	externalserviceconfig "google.golang.org/grpc/serviceconfig"
+)
+
+var logger = grpclog.Component("core")
+
+// BalancerConfig wraps the name and config associated with one load balancing
+// policy. It corresponds to a single entry of the loadBalancingConfig field
+// from ServiceConfig.
+//
+// It implements the json.Unmarshaler interface.
+//
+// https://github.com/grpc/grpc-proto/blob/54713b1e8bc6ed2d4f25fb4dff527842150b91b2/grpc/service_config/service_config.proto#L247
+type BalancerConfig struct {
+	Name   string
+	Config externalserviceconfig.LoadBalancingConfig
+}
+
+type intermediateBalancerConfig []map[string]json.RawMessage
+
+// MarshalJSON implements the json.Marshaler interface.
+//
+// It marshals the balancer and config into a length-1 slice
+// ([]map[string]config).
+func (bc *BalancerConfig) MarshalJSON() ([]byte, error) {
+	if bc.Config == nil {
+		// If config is nil, return empty config `{}`.
+		return []byte(fmt.Sprintf(`[{%q: %v}]`, bc.Name, "{}")), nil
+	}
+	c, err := json.Marshal(bc.Config)
+	if err != nil {
+		return nil, err
+	}
+	return []byte(fmt.Sprintf(`[{%q: %s}]`, bc.Name, c)), nil
+}
+
+// UnmarshalJSON implements the json.Unmarshaler interface.
+//
+// ServiceConfig contains a list of loadBalancingConfigs, each with a name and
+// config. This method iterates through that list in order, and stops at the
+// first policy that is supported.
+// - If the config for the first supported policy is invalid, the whole service
+//   config is invalid.
+// - If the list doesn't contain any supported policy, the whole service config
+//   is invalid.
+func (bc *BalancerConfig) UnmarshalJSON(b []byte) error {
+	var ir intermediateBalancerConfig
+	err := json.Unmarshal(b, &ir)
+	if err != nil {
+		return err
+	}
+
+	var names []string
+	for i, lbcfg := range ir {
+		if len(lbcfg) != 1 {
+			return fmt.Errorf("invalid loadBalancingConfig: entry %v does not contain exactly 1 policy/config pair: %q", i, lbcfg)
+		}
+
+		var (
+			name    string
+			jsonCfg json.RawMessage
+		)
+		// Get the key:value pair from the map. We have already made sure that
+		// the map contains a single entry.
+		for name, jsonCfg = range lbcfg {
+		}
+
+		names = append(names, name)
+		builder := balancer.Get(name)
+		if builder == nil {
+			// If the balancer is not registered, move on to the next config.
+			// This is not an error.
+			continue
+		}
+		bc.Name = name
+
+		parser, ok := builder.(balancer.ConfigParser)
+		if !ok {
+			if string(jsonCfg) != "{}" {
+				logger.Warningf("non-empty balancer configuration %q, but balancer does not implement ParseConfig", string(jsonCfg))
+			}
+			// Stop at this, though the builder doesn't support parsing config.
+			return nil
+		}
+
+		cfg, err := parser.ParseConfig(jsonCfg)
+		if err != nil {
+			return fmt.Errorf("error parsing loadBalancingConfig for policy %q: %v", name, err)
+		}
+		bc.Config = cfg
+		return nil
+	}
+	// This is reached when the for loop iterates over all entries, but didn't
+	// return. This means we had a loadBalancingConfig slice but did not
+	// encounter a registered policy. The config is considered invalid in this
+	// case.
+	return fmt.Errorf("invalid loadBalancingConfig: no supported policies found in %v", names)
+}
+
+// MethodConfig defines the configuration recommended by the service providers for a
+// particular method.
+type MethodConfig struct {
+	// WaitForReady indicates whether RPCs sent to this method should wait until
+	// the connection is ready by default (!failfast). The value specified via the
+	// gRPC client API will override the value set here.
+	WaitForReady *bool
+	// Timeout is the default timeout for RPCs sent to this method. The actual
+	// deadline used will be the minimum of the value specified here and the value
+	// set by the application via the gRPC client API.  If either one is not set,
+	// then the other will be used.  If neither is set, then the RPC has no deadline.
+	Timeout *time.Duration
+	// MaxReqSize is the maximum allowed payload size for an individual request in a
+	// stream (client->server) in bytes. The size which is measured is the serialized
+	// payload after per-message compression (but before stream compression) in bytes.
+	// The actual value used is the minimum of the value specified here and the value set
+	// by the application via the gRPC client API. If either one is not set, then the other
+	// will be used.  If neither is set, then the built-in default is used.
+	MaxReqSize *int
+	// MaxRespSize is the maximum allowed payload size for an individual response in a
+	// stream (server->client) in bytes.
+	MaxRespSize *int
+	// RetryPolicy configures retry options for the method.
+	RetryPolicy *RetryPolicy
+}
+
+// RetryPolicy defines the go-native version of the retry policy defined by the
+// service config here:
+// https://github.com/grpc/proposal/blob/master/A6-client-retries.md#integration-with-service-config
+type RetryPolicy struct {
+	// MaxAttempts is the maximum number of attempts, including the original RPC.
+	//
+	// This field is required and must be two or greater.
+	MaxAttempts int
+
+	// Exponential backoff parameters. The initial retry attempt will occur at
+	// random(0, initialBackoff). In general, the nth attempt will occur at
+	// random(0,
+	//   min(initialBackoff*backoffMultiplier**(n-1), maxBackoff)).
+	//
+	// These fields are required and must be greater than zero.
+	InitialBackoff    time.Duration
+	MaxBackoff        time.Duration
+	BackoffMultiplier float64
+
+	// The set of status codes which may be retried.
+	//
+	// Status codes are specified as strings, e.g., "UNAVAILABLE".
+	//
+	// This field is required and must be non-empty.
+	// Note: a set is used to store this for easy lookup.
+	RetryableStatusCodes map[codes.Code]bool
+}