diff --git a/metrics-server/vendor/github.com/modern-go/concurrent/.gitignore b/metrics-server/vendor/github.com/modern-go/concurrent/.gitignore
new file mode 100644
index 0000000..3f2bc47
--- /dev/null
+++ b/metrics-server/vendor/github.com/modern-go/concurrent/.gitignore
@@ -0,0 +1 @@
+/coverage.txt
diff --git a/metrics-server/vendor/github.com/modern-go/concurrent/.travis.yml b/metrics-server/vendor/github.com/modern-go/concurrent/.travis.yml
new file mode 100644
index 0000000..449e67c
--- /dev/null
+++ b/metrics-server/vendor/github.com/modern-go/concurrent/.travis.yml
@@ -0,0 +1,14 @@
+language: go
+
+go:
+  - 1.8.x
+  - 1.x
+
+before_install:
+  - go get -t -v ./...
+
+script:
+  - ./test.sh
+
+after_success:
+  - bash <(curl -s https://codecov.io/bash)
diff --git a/metrics-server/vendor/github.com/modern-go/concurrent/LICENSE b/metrics-server/vendor/github.com/modern-go/concurrent/LICENSE
new file mode 100644
index 0000000..261eeb9
--- /dev/null
+++ b/metrics-server/vendor/github.com/modern-go/concurrent/LICENSE
@@ -0,0 +1,201 @@
+                                 Apache License
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+                        http://www.apache.org/licenses/
+
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+
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diff --git a/metrics-server/vendor/github.com/modern-go/concurrent/README.md b/metrics-server/vendor/github.com/modern-go/concurrent/README.md
new file mode 100644
index 0000000..acab320
--- /dev/null
+++ b/metrics-server/vendor/github.com/modern-go/concurrent/README.md
@@ -0,0 +1,49 @@
+# concurrent
+
+[![Sourcegraph](https://sourcegraph.com/github.com/modern-go/concurrent/-/badge.svg)](https://sourcegraph.com/github.com/modern-go/concurrent?badge)
+[![GoDoc](http://img.shields.io/badge/go-documentation-blue.svg?style=flat-square)](http://godoc.org/github.com/modern-go/concurrent)
+[![Build Status](https://travis-ci.org/modern-go/concurrent.svg?branch=master)](https://travis-ci.org/modern-go/concurrent)
+[![codecov](https://codecov.io/gh/modern-go/concurrent/branch/master/graph/badge.svg)](https://codecov.io/gh/modern-go/concurrent)
+[![rcard](https://goreportcard.com/badge/github.com/modern-go/concurrent)](https://goreportcard.com/report/github.com/modern-go/concurrent)
+[![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://raw.githubusercontent.com/modern-go/concurrent/master/LICENSE)
+
+* concurrent.Map: backport sync.Map for go below 1.9
+* concurrent.Executor: goroutine with explicit ownership and cancellable
+
+# concurrent.Map
+
+because sync.Map is only available in go 1.9, we can use concurrent.Map to make code portable
+
+```go
+m := concurrent.NewMap()
+m.Store("hello", "world")
+elem, found := m.Load("hello")
+// elem will be "world"
+// found will be true
+```
+
+# concurrent.Executor
+
+```go
+executor := concurrent.NewUnboundedExecutor()
+executor.Go(func(ctx context.Context) {
+    everyMillisecond := time.NewTicker(time.Millisecond)
+    for {
+        select {
+        case <-ctx.Done():
+            fmt.Println("goroutine exited")
+            return
+        case <-everyMillisecond.C:
+            // do something
+        }
+    }
+})
+time.Sleep(time.Second)
+executor.StopAndWaitForever()
+fmt.Println("executor stopped")
+```
+
+attach goroutine to executor instance, so that we can
+
+* cancel it by stop the executor with Stop/StopAndWait/StopAndWaitForever
+* handle panic by callback: the default behavior will no longer crash your application
\ No newline at end of file
diff --git a/metrics-server/vendor/github.com/modern-go/concurrent/executor.go b/metrics-server/vendor/github.com/modern-go/concurrent/executor.go
new file mode 100644
index 0000000..623dba1
--- /dev/null
+++ b/metrics-server/vendor/github.com/modern-go/concurrent/executor.go
@@ -0,0 +1,14 @@
+package concurrent
+
+import "context"
+
+// Executor replace go keyword to start a new goroutine
+// the goroutine should cancel itself if the context passed in has been cancelled
+// the goroutine started by the executor, is owned by the executor
+// we can cancel all executors owned by the executor just by stop the executor itself
+// however Executor interface does not Stop method, the one starting and owning executor
+// should use the concrete type of executor, instead of this interface.
+type Executor interface {
+	// Go starts a new goroutine controlled by the context
+	Go(handler func(ctx context.Context))
+}
diff --git a/metrics-server/vendor/github.com/modern-go/concurrent/go_above_19.go b/metrics-server/vendor/github.com/modern-go/concurrent/go_above_19.go
new file mode 100644
index 0000000..aeabf8c
--- /dev/null
+++ b/metrics-server/vendor/github.com/modern-go/concurrent/go_above_19.go
@@ -0,0 +1,15 @@
+//+build go1.9
+
+package concurrent
+
+import "sync"
+
+// Map is a wrapper for sync.Map introduced in go1.9
+type Map struct {
+	sync.Map
+}
+
+// NewMap creates a thread safe Map
+func NewMap() *Map {
+	return &Map{}
+}
diff --git a/metrics-server/vendor/github.com/modern-go/concurrent/go_below_19.go b/metrics-server/vendor/github.com/modern-go/concurrent/go_below_19.go
new file mode 100644
index 0000000..b9c8df7
--- /dev/null
+++ b/metrics-server/vendor/github.com/modern-go/concurrent/go_below_19.go
@@ -0,0 +1,33 @@
+//+build !go1.9
+
+package concurrent
+
+import "sync"
+
+// Map implements a thread safe map for go version below 1.9 using mutex
+type Map struct {
+	lock sync.RWMutex
+	data map[interface{}]interface{}
+}
+
+// NewMap creates a thread safe map
+func NewMap() *Map {
+	return &Map{
+		data: make(map[interface{}]interface{}, 32),
+	}
+}
+
+// Load is same as sync.Map Load
+func (m *Map) Load(key interface{}) (elem interface{}, found bool) {
+	m.lock.RLock()
+	elem, found = m.data[key]
+	m.lock.RUnlock()
+	return
+}
+
+// Load is same as sync.Map Store
+func (m *Map) Store(key interface{}, elem interface{}) {
+	m.lock.Lock()
+	m.data[key] = elem
+	m.lock.Unlock()
+}
diff --git a/metrics-server/vendor/github.com/modern-go/concurrent/log.go b/metrics-server/vendor/github.com/modern-go/concurrent/log.go
new file mode 100644
index 0000000..9756fcc
--- /dev/null
+++ b/metrics-server/vendor/github.com/modern-go/concurrent/log.go
@@ -0,0 +1,13 @@
+package concurrent
+
+import (
+	"os"
+	"log"
+	"io/ioutil"
+)
+
+// ErrorLogger is used to print out error, can be set to writer other than stderr
+var ErrorLogger = log.New(os.Stderr, "", 0)
+
+// InfoLogger is used to print informational message, default to off
+var InfoLogger = log.New(ioutil.Discard, "", 0)
\ No newline at end of file
diff --git a/metrics-server/vendor/github.com/modern-go/concurrent/test.sh b/metrics-server/vendor/github.com/modern-go/concurrent/test.sh
new file mode 100755
index 0000000..d1e6b2e
--- /dev/null
+++ b/metrics-server/vendor/github.com/modern-go/concurrent/test.sh
@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+
+set -e
+echo "" > coverage.txt
+
+for d in $(go list ./... | grep -v vendor); do
+    go test -coverprofile=profile.out -coverpkg=github.com/modern-go/concurrent $d
+    if [ -f profile.out ]; then
+        cat profile.out >> coverage.txt
+        rm profile.out
+    fi
+done
diff --git a/metrics-server/vendor/github.com/modern-go/concurrent/unbounded_executor.go b/metrics-server/vendor/github.com/modern-go/concurrent/unbounded_executor.go
new file mode 100644
index 0000000..05a77dc
--- /dev/null
+++ b/metrics-server/vendor/github.com/modern-go/concurrent/unbounded_executor.go
@@ -0,0 +1,119 @@
+package concurrent
+
+import (
+	"context"
+	"fmt"
+	"runtime"
+	"runtime/debug"
+	"sync"
+	"time"
+	"reflect"
+)
+
+// HandlePanic logs goroutine panic by default
+var HandlePanic = func(recovered interface{}, funcName string) {
+	ErrorLogger.Println(fmt.Sprintf("%s panic: %v", funcName, recovered))
+	ErrorLogger.Println(string(debug.Stack()))
+}
+
+// UnboundedExecutor is a executor without limits on counts of alive goroutines
+// it tracks the goroutine started by it, and can cancel them when shutdown
+type UnboundedExecutor struct {
+	ctx                   context.Context
+	cancel                context.CancelFunc
+	activeGoroutinesMutex *sync.Mutex
+	activeGoroutines      map[string]int
+	HandlePanic           func(recovered interface{}, funcName string)
+}
+
+// GlobalUnboundedExecutor has the life cycle of the program itself
+// any goroutine want to be shutdown before main exit can be started from this executor
+// GlobalUnboundedExecutor expects the main function to call stop
+// it does not magically knows the main function exits
+var GlobalUnboundedExecutor = NewUnboundedExecutor()
+
+// NewUnboundedExecutor creates a new UnboundedExecutor,
+// UnboundedExecutor can not be created by &UnboundedExecutor{}
+// HandlePanic can be set with a callback to override global HandlePanic
+func NewUnboundedExecutor() *UnboundedExecutor {
+	ctx, cancel := context.WithCancel(context.TODO())
+	return &UnboundedExecutor{
+		ctx:                   ctx,
+		cancel:                cancel,
+		activeGoroutinesMutex: &sync.Mutex{},
+		activeGoroutines:      map[string]int{},
+	}
+}
+
+// Go starts a new goroutine and tracks its lifecycle.
+// Panic will be recovered and logged automatically, except for StopSignal
+func (executor *UnboundedExecutor) Go(handler func(ctx context.Context)) {
+	pc := reflect.ValueOf(handler).Pointer()
+	f := runtime.FuncForPC(pc)
+	funcName := f.Name()
+	file, line := f.FileLine(pc)
+	executor.activeGoroutinesMutex.Lock()
+	defer executor.activeGoroutinesMutex.Unlock()
+	startFrom := fmt.Sprintf("%s:%d", file, line)
+	executor.activeGoroutines[startFrom] += 1
+	go func() {
+		defer func() {
+			recovered := recover()
+			// if you want to quit a goroutine without trigger HandlePanic
+			// use runtime.Goexit() to quit
+			if recovered != nil {
+				if executor.HandlePanic == nil {
+					HandlePanic(recovered, funcName)
+				} else {
+					executor.HandlePanic(recovered, funcName)
+				}
+			}
+			executor.activeGoroutinesMutex.Lock()
+			executor.activeGoroutines[startFrom] -= 1
+			executor.activeGoroutinesMutex.Unlock()
+		}()
+		handler(executor.ctx)
+	}()
+}
+
+// Stop cancel all goroutines started by this executor without wait
+func (executor *UnboundedExecutor) Stop() {
+	executor.cancel()
+}
+
+// StopAndWaitForever cancel all goroutines started by this executor and
+// wait until all goroutines exited
+func (executor *UnboundedExecutor) StopAndWaitForever() {
+	executor.StopAndWait(context.Background())
+}
+
+// StopAndWait cancel all goroutines started by this executor and wait.
+// Wait can be cancelled by the context passed in.
+func (executor *UnboundedExecutor) StopAndWait(ctx context.Context) {
+	executor.cancel()
+	for {
+		oneHundredMilliseconds := time.NewTimer(time.Millisecond * 100)
+		select {
+		case <-oneHundredMilliseconds.C:
+			if executor.checkNoActiveGoroutines() {
+				return
+			}
+		case <-ctx.Done():
+			return
+		}
+	}
+}
+
+func (executor *UnboundedExecutor) checkNoActiveGoroutines() bool {
+	executor.activeGoroutinesMutex.Lock()
+	defer executor.activeGoroutinesMutex.Unlock()
+	for startFrom, count := range executor.activeGoroutines {
+		if count > 0 {
+			InfoLogger.Println("UnboundedExecutor is still waiting goroutines to quit",
+				"startFrom", startFrom,
+				"count", count)
+			return false
+		}
+	}
+	return true
+}