Use caddy's certmagic library for extensible/robust ACME handling (#14177)

* use certmagic for more extensible/robust ACME cert handling

* accept TOS based on config option

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lauris BH <lauris@nix.lv>

12 files changed, 727 insertions, 0 deletions

diff --git a/vendor/go.uber.org/atomic/.codecov.yml b/vendor/go.uber.org/atomic/.codecov.yml
new file mode 100644
index 0000000000..6d4d1be7b5
--- /dev/null
+++ b/vendor/go.uber.org/atomic/.codecov.yml
@@ -0,0 +1,15 @@
+coverage:
+  range: 80..100
+  round: down
+  precision: 2
+
+  status:
+    project:                   # measuring the overall project coverage
+      default:                 # context, you can create multiple ones with custom titles
+        enabled: yes           # must be yes|true to enable this status
+        target: 100            # specify the target coverage for each commit status
+                               #   option: "auto" (must increase from parent commit or pull request base)
+                               #   option: "X%" a static target percentage to hit
+        if_not_found: success  # if parent is not found report status as success, error, or failure
+        if_ci_failed: error    # if ci fails report status as success, error, or failure
+
diff --git a/vendor/go.uber.org/atomic/.gitignore b/vendor/go.uber.org/atomic/.gitignore
new file mode 100644
index 0000000000..c3fa253893
--- /dev/null
+++ b/vendor/go.uber.org/atomic/.gitignore
@@ -0,0 +1,12 @@
+/bin
+.DS_Store
+/vendor
+cover.html
+cover.out
+lint.log
+
+# Binaries
+*.test
+
+# Profiling output
+*.prof
diff --git a/vendor/go.uber.org/atomic/.travis.yml b/vendor/go.uber.org/atomic/.travis.yml
new file mode 100644
index 0000000000..4e73268b60
--- /dev/null
+++ b/vendor/go.uber.org/atomic/.travis.yml
@@ -0,0 +1,27 @@
+sudo: false
+language: go
+go_import_path: go.uber.org/atomic
+
+env:
+  global:
+    - GO111MODULE=on
+
+matrix:
+  include:
+  - go: 1.12.x
+  - go: 1.13.x
+    env: LINT=1
+
+cache:
+  directories:
+    - vendor
+
+before_install:
+  - go version
+
+script:
+  - test -z "$LINT" || make lint
+  - make cover
+
+after_success:
+  - bash <(curl -s https://codecov.io/bash)
diff --git a/vendor/go.uber.org/atomic/CHANGELOG.md b/vendor/go.uber.org/atomic/CHANGELOG.md
new file mode 100644
index 0000000000..aef8b6ebc4
--- /dev/null
+++ b/vendor/go.uber.org/atomic/CHANGELOG.md
@@ -0,0 +1,64 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [1.6.0] - 2020-02-24
+### Changed
+- Drop library dependency on `golang.org/x/{lint, tools}`.
+
+## [1.5.1] - 2019-11-19
+- Fix bug where `Bool.CAS` and `Bool.Toggle` do work correctly together
+  causing `CAS` to fail even though the old value matches.
+
+## [1.5.0] - 2019-10-29
+### Changed
+- With Go modules, only the `go.uber.org/atomic` import path is supported now.
+  If you need to use the old import path, please add a `replace` directive to
+  your `go.mod`.
+
+## [1.4.0] - 2019-05-01
+### Added
+ - Add `atomic.Error` type for atomic operations on `error` values.
+
+## [1.3.2] - 2018-05-02
+### Added
+- Add `atomic.Duration` type for atomic operations on `time.Duration` values.
+
+## [1.3.1] - 2017-11-14
+### Fixed
+- Revert optimization for `atomic.String.Store("")` which caused data races.
+
+## [1.3.0] - 2017-11-13
+### Added
+- Add `atomic.Bool.CAS` for compare-and-swap semantics on bools.
+
+### Changed
+- Optimize `atomic.String.Store("")` by avoiding an allocation.
+
+## [1.2.0] - 2017-04-12
+### Added
+- Shadow `atomic.Value` from `sync/atomic`.
+
+## [1.1.0] - 2017-03-10
+### Added
+- Add atomic `Float64` type.
+
+### Changed
+- Support new `go.uber.org/atomic` import path.
+
+## [1.0.0] - 2016-07-18
+
+- Initial release.
+
+[1.6.0]: https://github.com/uber-go/atomic/compare/v1.5.1...v1.6.0
+[1.5.1]: https://github.com/uber-go/atomic/compare/v1.5.0...v1.5.1
+[1.5.0]: https://github.com/uber-go/atomic/compare/v1.4.0...v1.5.0
+[1.4.0]: https://github.com/uber-go/atomic/compare/v1.3.2...v1.4.0
+[1.3.2]: https://github.com/uber-go/atomic/compare/v1.3.1...v1.3.2
+[1.3.1]: https://github.com/uber-go/atomic/compare/v1.3.0...v1.3.1
+[1.3.0]: https://github.com/uber-go/atomic/compare/v1.2.0...v1.3.0
+[1.2.0]: https://github.com/uber-go/atomic/compare/v1.1.0...v1.2.0
+[1.1.0]: https://github.com/uber-go/atomic/compare/v1.0.0...v1.1.0
+[1.0.0]: https://github.com/uber-go/atomic/releases/tag/v1.0.0
diff --git a/vendor/go.uber.org/atomic/LICENSE.txt b/vendor/go.uber.org/atomic/LICENSE.txt
new file mode 100644
index 0000000000..8765c9fbc6
--- /dev/null
+++ b/vendor/go.uber.org/atomic/LICENSE.txt
@@ -0,0 +1,19 @@
+Copyright (c) 2016 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
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
diff --git a/vendor/go.uber.org/atomic/Makefile b/vendor/go.uber.org/atomic/Makefile
new file mode 100644
index 0000000000..39af0fb63f
--- /dev/null
+++ b/vendor/go.uber.org/atomic/Makefile
@@ -0,0 +1,35 @@
+# Directory to place `go install`ed binaries into.
+export GOBIN ?= $(shell pwd)/bin
+
+GOLINT = $(GOBIN)/golint
+
+GO_FILES ?= *.go
+
+.PHONY: build
+build:
+	go build ./...
+
+.PHONY: test
+test:
+	go test -race ./...
+
+.PHONY: gofmt
+gofmt:
+	$(eval FMT_LOG := $(shell mktemp -t gofmt.XXXXX))
+	gofmt -e -s -l $(GO_FILES) > $(FMT_LOG) || true
+	@[ ! -s "$(FMT_LOG)" ] || (echo "gofmt failed:" && cat $(FMT_LOG) && false)
+
+$(GOLINT):
+	go install golang.org/x/lint/golint
+
+.PHONY: golint
+golint: $(GOLINT)
+	$(GOLINT) ./...
+
+.PHONY: lint
+lint: gofmt golint
+
+.PHONY: cover
+cover:
+	go test -coverprofile=cover.out -coverpkg ./... -v ./...
+	go tool cover -html=cover.out -o cover.html
diff --git a/vendor/go.uber.org/atomic/README.md b/vendor/go.uber.org/atomic/README.md
new file mode 100644
index 0000000000..ade0c20f16
--- /dev/null
+++ b/vendor/go.uber.org/atomic/README.md
@@ -0,0 +1,63 @@
+# atomic [![GoDoc][doc-img]][doc] [![Build Status][ci-img]][ci] [![Coverage Status][cov-img]][cov] [![Go Report Card][reportcard-img]][reportcard]
+
+Simple wrappers for primitive types to enforce atomic access.
+
+## Installation
+
+```shell
+$ go get -u go.uber.org/atomic@v1
+```
+
+### Legacy Import Path
+
+As of v1.5.0, the import path `go.uber.org/atomic` is the only supported way
+of using this package. If you are using Go modules, this package will fail to
+compile with the legacy import path path `github.com/uber-go/atomic`.
+
+We recommend migrating your code to the new import path but if you're unable
+to do so, or if your dependencies are still using the old import path, you
+will have to add a `replace` directive to your `go.mod` file downgrading the
+legacy import path to an older version.
+
+```
+replace github.com/uber-go/atomic => github.com/uber-go/atomic v1.4.0
+```
+
+You can do so automatically by running the following command.
+
+```shell
+$ go mod edit -replace github.com/uber-go/atomic=github.com/uber-go/atomic@v1.4.0
+```
+
+## Usage
+
+The standard library's `sync/atomic` is powerful, but it's easy to forget which
+variables must be accessed atomically. `go.uber.org/atomic` preserves all the
+functionality of the standard library, but wraps the primitive types to
+provide a safer, more convenient API.
+
+```go
+var atom atomic.Uint32
+atom.Store(42)
+atom.Sub(2)
+atom.CAS(40, 11)
+```
+
+See the [documentation][doc] for a complete API specification.
+
+## Development Status
+
+Stable.
+
+---
+
+Released under the [MIT License](LICENSE.txt).
+
+[doc-img]: https://godoc.org/github.com/uber-go/atomic?status.svg
+[doc]: https://godoc.org/go.uber.org/atomic
+[ci-img]: https://travis-ci.com/uber-go/atomic.svg?branch=master
+[ci]: https://travis-ci.com/uber-go/atomic
+[cov-img]: https://codecov.io/gh/uber-go/atomic/branch/master/graph/badge.svg
+[cov]: https://codecov.io/gh/uber-go/atomic
+[reportcard-img]: https://goreportcard.com/badge/go.uber.org/atomic
+[reportcard]: https://goreportcard.com/report/go.uber.org/atomic
diff --git a/vendor/go.uber.org/atomic/atomic.go b/vendor/go.uber.org/atomic/atomic.go
new file mode 100644
index 0000000000..ad5fa0980a
--- /dev/null
+++ b/vendor/go.uber.org/atomic/atomic.go
@@ -0,0 +1,356 @@
+// Copyright (c) 2016 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
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+// Package atomic provides simple wrappers around numerics to enforce atomic
+// access.
+package atomic
+
+import (
+	"math"
+	"sync/atomic"
+	"time"
+)
+
+// Int32 is an atomic wrapper around an int32.
+type Int32 struct{ v int32 }
+
+// NewInt32 creates an Int32.
+func NewInt32(i int32) *Int32 {
+	return &Int32{i}
+}
+
+// Load atomically loads the wrapped value.
+func (i *Int32) Load() int32 {
+	return atomic.LoadInt32(&i.v)
+}
+
+// Add atomically adds to the wrapped int32 and returns the new value.
+func (i *Int32) Add(n int32) int32 {
+	return atomic.AddInt32(&i.v, n)
+}
+
+// Sub atomically subtracts from the wrapped int32 and returns the new value.
+func (i *Int32) Sub(n int32) int32 {
+	return atomic.AddInt32(&i.v, -n)
+}
+
+// Inc atomically increments the wrapped int32 and returns the new value.
+func (i *Int32) Inc() int32 {
+	return i.Add(1)
+}
+
+// Dec atomically decrements the wrapped int32 and returns the new value.
+func (i *Int32) Dec() int32 {
+	return i.Sub(1)
+}
+
+// CAS is an atomic compare-and-swap.
+func (i *Int32) CAS(old, new int32) bool {
+	return atomic.CompareAndSwapInt32(&i.v, old, new)
+}
+
+// Store atomically stores the passed value.
+func (i *Int32) Store(n int32) {
+	atomic.StoreInt32(&i.v, n)
+}
+
+// Swap atomically swaps the wrapped int32 and returns the old value.
+func (i *Int32) Swap(n int32) int32 {
+	return atomic.SwapInt32(&i.v, n)
+}
+
+// Int64 is an atomic wrapper around an int64.
+type Int64 struct{ v int64 }
+
+// NewInt64 creates an Int64.
+func NewInt64(i int64) *Int64 {
+	return &Int64{i}
+}
+
+// Load atomically loads the wrapped value.
+func (i *Int64) Load() int64 {
+	return atomic.LoadInt64(&i.v)
+}
+
+// Add atomically adds to the wrapped int64 and returns the new value.
+func (i *Int64) Add(n int64) int64 {
+	return atomic.AddInt64(&i.v, n)
+}
+
+// Sub atomically subtracts from the wrapped int64 and returns the new value.
+func (i *Int64) Sub(n int64) int64 {
+	return atomic.AddInt64(&i.v, -n)
+}
+
+// Inc atomically increments the wrapped int64 and returns the new value.
+func (i *Int64) Inc() int64 {
+	return i.Add(1)
+}
+
+// Dec atomically decrements the wrapped int64 and returns the new value.
+func (i *Int64) Dec() int64 {
+	return i.Sub(1)
+}
+
+// CAS is an atomic compare-and-swap.
+func (i *Int64) CAS(old, new int64) bool {
+	return atomic.CompareAndSwapInt64(&i.v, old, new)
+}
+
+// Store atomically stores the passed value.
+func (i *Int64) Store(n int64) {
+	atomic.StoreInt64(&i.v, n)
+}
+
+// Swap atomically swaps the wrapped int64 and returns the old value.
+func (i *Int64) Swap(n int64) int64 {
+	return atomic.SwapInt64(&i.v, n)
+}
+
+// Uint32 is an atomic wrapper around an uint32.
+type Uint32 struct{ v uint32 }
+
+// NewUint32 creates a Uint32.
+func NewUint32(i uint32) *Uint32 {
+	return &Uint32{i}
+}
+
+// Load atomically loads the wrapped value.
+func (i *Uint32) Load() uint32 {
+	return atomic.LoadUint32(&i.v)
+}
+
+// Add atomically adds to the wrapped uint32 and returns the new value.
+func (i *Uint32) Add(n uint32) uint32 {
+	return atomic.AddUint32(&i.v, n)
+}
+
+// Sub atomically subtracts from the wrapped uint32 and returns the new value.
+func (i *Uint32) Sub(n uint32) uint32 {
+	return atomic.AddUint32(&i.v, ^(n - 1))
+}
+
+// Inc atomically increments the wrapped uint32 and returns the new value.
+func (i *Uint32) Inc() uint32 {
+	return i.Add(1)
+}
+
+// Dec atomically decrements the wrapped int32 and returns the new value.
+func (i *Uint32) Dec() uint32 {
+	return i.Sub(1)
+}
+
+// CAS is an atomic compare-and-swap.
+func (i *Uint32) CAS(old, new uint32) bool {
+	return atomic.CompareAndSwapUint32(&i.v, old, new)
+}
+
+// Store atomically stores the passed value.
+func (i *Uint32) Store(n uint32) {
+	atomic.StoreUint32(&i.v, n)
+}
+
+// Swap atomically swaps the wrapped uint32 and returns the old value.
+func (i *Uint32) Swap(n uint32) uint32 {
+	return atomic.SwapUint32(&i.v, n)
+}
+
+// Uint64 is an atomic wrapper around a uint64.
+type Uint64 struct{ v uint64 }
+
+// NewUint64 creates a Uint64.
+func NewUint64(i uint64) *Uint64 {
+	return &Uint64{i}
+}
+
+// Load atomically loads the wrapped value.
+func (i *Uint64) Load() uint64 {
+	return atomic.LoadUint64(&i.v)
+}
+
+// Add atomically adds to the wrapped uint64 and returns the new value.
+func (i *Uint64) Add(n uint64) uint64 {
+	return atomic.AddUint64(&i.v, n)
+}
+
+// Sub atomically subtracts from the wrapped uint64 and returns the new value.
+func (i *Uint64) Sub(n uint64) uint64 {
+	return atomic.AddUint64(&i.v, ^(n - 1))
+}
+
+// Inc atomically increments the wrapped uint64 and returns the new value.
+func (i *Uint64) Inc() uint64 {
+	return i.Add(1)
+}
+
+// Dec atomically decrements the wrapped uint64 and returns the new value.
+func (i *Uint64) Dec() uint64 {
+	return i.Sub(1)
+}
+
+// CAS is an atomic compare-and-swap.
+func (i *Uint64) CAS(old, new uint64) bool {
+	return atomic.CompareAndSwapUint64(&i.v, old, new)
+}
+
+// Store atomically stores the passed value.
+func (i *Uint64) Store(n uint64) {
+	atomic.StoreUint64(&i.v, n)
+}
+
+// Swap atomically swaps the wrapped uint64 and returns the old value.
+func (i *Uint64) Swap(n uint64) uint64 {
+	return atomic.SwapUint64(&i.v, n)
+}
+
+// Bool is an atomic Boolean.
+type Bool struct{ v uint32 }
+
+// NewBool creates a Bool.
+func NewBool(initial bool) *Bool {
+	return &Bool{boolToInt(initial)}
+}
+
+// Load atomically loads the Boolean.
+func (b *Bool) Load() bool {
+	return truthy(atomic.LoadUint32(&b.v))
+}
+
+// CAS is an atomic compare-and-swap.
+func (b *Bool) CAS(old, new bool) bool {
+	return atomic.CompareAndSwapUint32(&b.v, boolToInt(old), boolToInt(new))
+}
+
+// Store atomically stores the passed value.
+func (b *Bool) Store(new bool) {
+	atomic.StoreUint32(&b.v, boolToInt(new))
+}
+
+// Swap sets the given value and returns the previous value.
+func (b *Bool) Swap(new bool) bool {
+	return truthy(atomic.SwapUint32(&b.v, boolToInt(new)))
+}
+
+// Toggle atomically negates the Boolean and returns the previous value.
+func (b *Bool) Toggle() bool {
+	for {
+		old := b.Load()
+		if b.CAS(old, !old) {
+			return old
+		}
+	}
+}
+
+func truthy(n uint32) bool {
+	return n == 1
+}
+
+func boolToInt(b bool) uint32 {
+	if b {
+		return 1
+	}
+	return 0
+}
+
+// Float64 is an atomic wrapper around float64.
+type Float64 struct {
+	v uint64
+}
+
+// NewFloat64 creates a Float64.
+func NewFloat64(f float64) *Float64 {
+	return &Float64{math.Float64bits(f)}
+}
+
+// Load atomically loads the wrapped value.
+func (f *Float64) Load() float64 {
+	return math.Float64frombits(atomic.LoadUint64(&f.v))
+}
+
+// Store atomically stores the passed value.
+func (f *Float64) Store(s float64) {
+	atomic.StoreUint64(&f.v, math.Float64bits(s))
+}
+
+// Add atomically adds to the wrapped float64 and returns the new value.
+func (f *Float64) Add(s float64) float64 {
+	for {
+		old := f.Load()
+		new := old + s
+		if f.CAS(old, new) {
+			return new
+		}
+	}
+}
+
+// Sub atomically subtracts from the wrapped float64 and returns the new value.
+func (f *Float64) Sub(s float64) float64 {
+	return f.Add(-s)
+}
+
+// CAS is an atomic compare-and-swap.
+func (f *Float64) CAS(old, new float64) bool {
+	return atomic.CompareAndSwapUint64(&f.v, math.Float64bits(old), math.Float64bits(new))
+}
+
+// Duration is an atomic wrapper around time.Duration
+// https://godoc.org/time#Duration
+type Duration struct {
+	v Int64
+}
+
+// NewDuration creates a Duration.
+func NewDuration(d time.Duration) *Duration {
+	return &Duration{v: *NewInt64(int64(d))}
+}
+
+// Load atomically loads the wrapped value.
+func (d *Duration) Load() time.Duration {
+	return time.Duration(d.v.Load())
+}
+
+// Store atomically stores the passed value.
+func (d *Duration) Store(n time.Duration) {
+	d.v.Store(int64(n))
+}
+
+// Add atomically adds to the wrapped time.Duration and returns the new value.
+func (d *Duration) Add(n time.Duration) time.Duration {
+	return time.Duration(d.v.Add(int64(n)))
+}
+
+// Sub atomically subtracts from the wrapped time.Duration and returns the new value.
+func (d *Duration) Sub(n time.Duration) time.Duration {
+	return time.Duration(d.v.Sub(int64(n)))
+}
+
+// Swap atomically swaps the wrapped time.Duration and returns the old value.
+func (d *Duration) Swap(n time.Duration) time.Duration {
+	return time.Duration(d.v.Swap(int64(n)))
+}
+
+// CAS is an atomic compare-and-swap.
+func (d *Duration) CAS(old, new time.Duration) bool {
+	return d.v.CAS(int64(old), int64(new))
+}
+
+// Value shadows the type of the same name from sync/atomic
+// https://godoc.org/sync/atomic#Value
+type Value struct{ atomic.Value }
diff --git a/vendor/go.uber.org/atomic/error.go b/vendor/go.uber.org/atomic/error.go
new file mode 100644
index 0000000000..0489d19bad
--- /dev/null
+++ b/vendor/go.uber.org/atomic/error.go
@@ -0,0 +1,55 @@
+// Copyright (c) 2016 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
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+package atomic
+
+// Error is an atomic type-safe wrapper around Value for errors
+type Error struct{ v Value }
+
+// errorHolder is non-nil holder for error object.
+// atomic.Value panics on saving nil object, so err object needs to be
+// wrapped with valid object first.
+type errorHolder struct{ err error }
+
+// NewError creates new atomic error object
+func NewError(err error) *Error {
+	e := &Error{}
+	if err != nil {
+		e.Store(err)
+	}
+	return e
+}
+
+// Load atomically loads the wrapped error
+func (e *Error) Load() error {
+	v := e.v.Load()
+	if v == nil {
+		return nil
+	}
+
+	eh := v.(errorHolder)
+	return eh.err
+}
+
+// Store atomically stores error.
+// NOTE: a holder object is allocated on each Store call.
+func (e *Error) Store(err error) {
+	e.v.Store(errorHolder{err: err})
+}
diff --git a/vendor/go.uber.org/atomic/go.mod b/vendor/go.uber.org/atomic/go.mod
new file mode 100644
index 0000000000..a935daebb9
--- /dev/null
+++ b/vendor/go.uber.org/atomic/go.mod
@@ -0,0 +1,10 @@
+module go.uber.org/atomic
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/stretchr/testify v1.3.0
+	golang.org/x/lint v0.0.0-20190930215403-16217165b5de
+	golang.org/x/tools v0.0.0-20191029041327-9cc4af7d6b2c // indirect
+)
+
+go 1.13
diff --git a/vendor/go.uber.org/atomic/go.sum b/vendor/go.uber.org/atomic/go.sum
new file mode 100644
index 0000000000..51b2b62afb
--- /dev/null
+++ b/vendor/go.uber.org/atomic/go.sum
@@ -0,0 +1,22 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
+github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/lint v0.0.0-20190930215403-16217165b5de h1:5hukYrvBGR8/eNkX5mdUezrA6JiaEZDtJb9Ei+1LlBs=
+golang.org/x/lint v0.0.0-20190930215403-16217165b5de/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=
+golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/tools v0.0.0-20190311212946-11955173bddd h1:/e+gpKk9r3dJobndpTytxS2gOy6m5uvpg+ISQoEcusQ=
+golang.org/x/tools v0.0.0-20190311212946-11955173bddd/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
+golang.org/x/tools v0.0.0-20191029041327-9cc4af7d6b2c h1:IGkKhmfzcztjm6gYkykvu/NiS8kaqbCWAEWWAyf8J5U=
+golang.org/x/tools v0.0.0-20191029041327-9cc4af7d6b2c/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
diff --git a/vendor/go.uber.org/atomic/string.go b/vendor/go.uber.org/atomic/string.go
new file mode 100644
index 0000000000..ede8136fac
--- /dev/null
+++ b/vendor/go.uber.org/atomic/string.go
@@ -0,0 +1,49 @@
+// Copyright (c) 2016 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
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+package atomic
+
+// String is an atomic type-safe wrapper around Value for strings.
+type String struct{ v Value }
+
+// NewString creates a String.
+func NewString(str string) *String {
+	s := &String{}
+	if str != "" {
+		s.Store(str)
+	}
+	return s
+}
+
+// Load atomically loads the wrapped string.
+func (s *String) Load() string {
+	v := s.v.Load()
+	if v == nil {
+		return ""
+	}
+	return v.(string)
+}
+
+// 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)
+}