added vendors

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()
+}