Added Set data structure. This caused by fact that two NS may have same domains

dnsexit_manager.go

@@ -132,7 +132,7 @@ func (c *client) UpdateRecord(rec *dns.Record) (error, *dns.Response) {
 }
 
 func (c *client) GetRecords() (error, []*dns.Record) {
-	var subdomains []*dns.Record
+	var subdomains = CreateSet()
 	var wg sync.WaitGroup
 
 	result_chan := make(chan []*dns.Record)
@@ -169,10 +169,12 @@ func (c *client) GetRecords() (error, []*dns.Record) {
 		select {
 		case records, ok := <-result_chan:
 			if !ok {
-				return nil, subdomains
+				return nil, subdomains.List()
 			}
       
-			subdomains = append(subdomains, records...)
+      for record := range records {
+        subdomains.Add(record)
+      }
 			case _, _ = <-err_chan:
 		}
 	}

set.go

@@ -0,0 +1,33 @@
+package dnsexit_manager
+
+
+type Set struct {
+  elements map[interface{}]struct{}
+}
+
+func CreateSet() *Set {
+  return &Set{
+    elements: make(map[interface{}]struct{}),
+  }
+}
+
+func (set *Set) Add(value interface{}) {
+  _, found := set.elements[value]
+  
+  if !found{
+    set.elements[value] = struct{}{}
+  }
+}
+
+func (set *Set) Delete(value interface{}) {
+  delete(set.elements, value)
+}
+
+func (set *Set) List() []interface{} {
+  keys := make([]interface{}, 0, len(set.elements))
+  for key := range set.elements {
+    keys = append(keys, key)
+  }
+
+  return keys
+}