Update vendor for next release (#1343)

vendor/go.uber.org/atomic/string.go

@@ -1,4 +1,6 @@
-// Copyright (c) 2016 Uber Technologies, Inc.
+// @generated Code generated by gen-atomicwrapper.
+
+// Copyright (c) 2020 Uber Technologies, Inc.
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
 // of this software and associated documentation files (the "Software"), to deal
@@ -20,30 +22,33 @@
 
 package atomic
 
-// String is an atomic type-safe wrapper around Value for strings.
-type String struct{ v Value }
+// String is an atomic type-safe wrapper for string values.
+type String struct {
+	_ nocmp // disallow non-atomic comparison
 
-// NewString creates a String.
-func NewString(str string) *String {
-	s := &String{}
-	if str != "" {
-		s.Store(str)
+	v Value
+}
+
+var _zeroString string
+
+// NewString creates a new String.
+func NewString(v string) *String {
+	x := &String{}
+	if v != _zeroString {
+		x.Store(v)
 	}
-	return s
+	return x
 }
 
 // Load atomically loads the wrapped string.
-func (s *String) Load() string {
-	v := s.v.Load()
-	if v == nil {
-		return ""
+func (x *String) Load() string {
+	if v := x.v.Load(); v != nil {
+		return v.(string)
 	}
-	return v.(string)
+	return _zeroString
 }
 
 // Store atomically stores the passed string.
-// Note: Converting the string to an interface{} to store in the Value
-// requires an allocation.
-func (s *String) Store(str string) {
-	s.v.Store(str)
+func (x *String) Store(v string) {
+	x.v.Store(v)
 }