diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/fieldextractor.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/fieldextractor.go
new file mode 100644
index 0000000..549ff48
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/tags/fieldextractor.go
@@ -0,0 +1,85 @@
+// Copyright 2017 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+package grpc_ctxtags
+
+import (
+	"reflect"
+)
+
+// RequestFieldExtractorFunc is a user-provided function that extracts field information from a gRPC request.
+// It is called from tags middleware on arrival of unary request or a server-stream request.
+// Keys and values will be added to the context tags of the request. If there are no fields, you should return a nil.
+type RequestFieldExtractorFunc func(fullMethod string, req interface{}) map[string]interface{}
+
+type requestFieldsExtractor interface {
+	// ExtractRequestFields is a method declared on a Protobuf message that extracts fields from the interface.
+	// The values from the extracted fields should be set in the appendToMap, in order to avoid allocations.
+	ExtractRequestFields(appendToMap map[string]interface{})
+}
+
+// CodeGenRequestFieldExtractor is a function that relies on code-generated functions that export log fields from requests.
+// These are usually coming from a protoc-plugin that generates additional information based on custom field options.
+func CodeGenRequestFieldExtractor(fullMethod string, req interface{}) map[string]interface{} {
+	if ext, ok := req.(requestFieldsExtractor); ok {
+		retMap := make(map[string]interface{})
+		ext.ExtractRequestFields(retMap)
+		if len(retMap) == 0 {
+			return nil
+		}
+		return retMap
+	}
+	return nil
+}
+
+// TagBasedRequestFieldExtractor is a function that relies on Go struct tags to export log fields from requests.
+// These are usually coming from a protoc-plugin, such as Gogo protobuf.
+//
+//  message Metadata {
+//     repeated string tags = 1 [ (gogoproto.moretags) = "log_field:\"meta_tags\"" ];
+//  }
+//
+// The tagName is configurable using the tagName variable. Here it would be "log_field".
+func TagBasedRequestFieldExtractor(tagName string) RequestFieldExtractorFunc {
+	return func(fullMethod string, req interface{}) map[string]interface{} {
+		retMap := make(map[string]interface{})
+		reflectMessageTags(req, retMap, tagName)
+		if len(retMap) == 0 {
+			return nil
+		}
+		return retMap
+	}
+}
+
+func reflectMessageTags(msg interface{}, existingMap map[string]interface{}, tagName string) {
+	v := reflect.ValueOf(msg)
+	// Only deal with pointers to structs.
+	if v.Kind() != reflect.Ptr || v.Elem().Kind() != reflect.Struct {
+		return
+	}
+	// Deref the pointer get to the struct.
+	v = v.Elem()
+	t := v.Type()
+	for i := 0; i < v.NumField(); i++ {
+		field := v.Field(i)
+		kind := field.Kind()
+		// Only recurse down direct pointers, which should only be to nested structs.
+		if kind == reflect.Ptr {
+			reflectMessageTags(field.Interface(), existingMap, tagName)
+		}
+		// In case of arrays/splices (repeated fields) go down to the concrete type.
+		if kind == reflect.Array || kind == reflect.Slice {
+			if field.Len() == 0 {
+				continue
+			}
+			kind = field.Index(0).Kind()
+		}
+		// Only be interested in
+		if (kind >= reflect.Bool && kind <= reflect.Float64) || kind == reflect.String {
+			if tag := t.Field(i).Tag.Get(tagName); tag != "" {
+				existingMap[tag] = field.Interface()
+			}
+		}
+	}
+	return
+}