diff --git a/collections/queue/queue.go b/collections/queue/queue.go
index 4457963..6658a32 100644
--- a/collections/queue/queue.go
+++ b/collections/queue/queue.go
@@ -1,26 +1,26 @@
 package queue
 
 type Queue struct {
-	queue []interface{}
+    queue []interface{}
     len int
 }
 
 func New() *Queue {
-	queue := &Queue{}
-	queue.queue = make([]interface{}, 0)
+    queue := &Queue{}
+    queue.queue = make([]interface{}, 0)
     queue.len = 0
     return queue
 }
 
 func (queue *Queue) Length() int {
-	return queue.len
+    return queue.len
 }
 
 func (q *Queue) Remove() interface{} {
-	tmp := q.queue[0]
-	q.queue = q.queue[1:]
-	q.len -= 1
-	return tmp
+    tmp := q.queue[0]
+    q.queue = q.queue[1:]
+    q.len -= 1
+    return tmp
 }
 
 func (q *Queue) Peek() interface{} {
@@ -28,6 +28,6 @@ func (q *Queue) Peek() interface{} {
 }
 
 func (q *Queue) Add(value interface{}) {
-	q.len += 1
-	q.queue = append(q.queue, value)
+    q.len += 1
+    q.queue = append(q.queue, value)
 } 
diff --git a/collections/queue/queue_test.go b/collections/queue/queue_test.go
index f96041b..32361cf 100644
--- a/collections/queue/queue_test.go
+++ b/collections/queue/queue_test.go
@@ -3,27 +3,27 @@ package queue
 import "testing"
 
 func Test_Queue(t *testing.T) {
-	queue := New()
+    queue := New()
 
-	queue.Add(1)
-	queue.Add(2)
-	queue.Add(3)
+    queue.Add(1)
+    queue.Add(2)
+    queue.Add(3)
 
-	if queue.Length() != 3 {
-		t.Error("[Error] queue length is wrong")
-	}
+    if queue.Length() != 3 {
+        t.Error("[Error] queue length is wrong")
+    }
 
     element := queue.Remove()
 
-	if element != 1 {
-		t.Error("[Error] remove is wrong")
-	}
+    if element != 1 {
+        t.Error("[Error] remove is wrong")
+    }
 
-	if queue.Length() != 2 {
-		t.Error("[Error] queue length is wrong after pop")
-	}
-	
-	if queue.Peek() != 2 {
-		t.Error("[Error] queue Peek is wrong")
-	}
+    if queue.Length() != 2 {
+        t.Error("[Error] queue length is wrong after pop")
+    }
+    
+    if queue.Peek() != 2 {
+        t.Error("[Error] queue Peek is wrong")
+    }
 }
diff --git a/collections/stack/stack.go b/collections/stack/stack.go
index 3e020cf..cc2af21 100644
--- a/collections/stack/stack.go
+++ b/collections/stack/stack.go
@@ -1,24 +1,24 @@
 package stack
 
 type Stack struct {
-	st []interface{}
+    st []interface{}
     len int
 }
 
 func New() *Stack {
-	stack := &Stack{}
-	stack.st = make([]interface{}, 1)
+    stack := &Stack{}
+    stack.st = make([]interface{}, 1)
     stack.len = 0
     return stack
 }
 
 func (stack *Stack) Length() int {
-	return stack.len
+    return stack.len
 }
 
 func (stack *Stack) Pop() {
-	stack.st = stack.st[1:]
-	stack.len -= 1
+    stack.st = stack.st[1:]
+    stack.len -= 1
 }
 
 func (stack *Stack) Peek() interface{} {
@@ -26,36 +26,36 @@ func (stack *Stack) Peek() interface{} {
 }
 
 func (stack *Stack) IsEmpty() bool {
-	return (stack.len == 0)
+    return (stack.len == 0)
 }
 
 func (stack *Stack) Push(value interface{}) {
-	stack.len += 1
-	add(stack, value)
+    stack.len += 1
+    add(stack, value)
 } 
 
 func add(slice *Stack, value interface{}) {
-	var tmpSlice []interface{} = make([]interface{}, slice.len)
-	if slice.len == 0 {
-		slice.st[0] = value
-		return
-	}
-	
-	for i:=0; i < slice.len; i++ {
-		tmpSlice[i] = 0
-	}
-	
-	for i:=0; i < slice.len; i++ {
-		if i == 0 {
-			tmpSlice[0] = value
-		} else {
-			tmpSlice[i] = slice.st[i - 1]
-		}
-
-		if i == slice.len - 1 {
-			break
-		}
-	}
-	
-	slice.st = tmpSlice
+    var tmpSlice []interface{} = make([]interface{}, slice.len)
+    if slice.len == 0 {
+        slice.st[0] = value
+        return
+    }
+    
+    for i:=0; i < slice.len; i++ {
+        tmpSlice[i] = 0
+    }
+    
+    for i:=0; i < slice.len; i++ {
+        if i == 0 {
+            tmpSlice[0] = value
+        } else {
+            tmpSlice[i] = slice.st[i - 1]
+        }
+
+        if i == slice.len - 1 {
+            break
+        }
+    }
+    
+    slice.st = tmpSlice
 }
diff --git a/collections/stack/stack_test.go b/collections/stack/stack_test.go
index bc97850..f5c87fd 100644
--- a/collections/stack/stack_test.go
+++ b/collections/stack/stack_test.go
@@ -3,23 +3,23 @@ package stack
 import "testing"
 
 func Test_Stack(t *testing.T) {
-	stack := New()
+    stack := New()
 
     stack.Push(5)
     stack.Push(6)
     stack.Push(7)
-	
-	if stack.Length() != 3 {
-		t.Error("[Error] stack length is wrong")
-	}
+    
+    if stack.Length() != 3 {
+        t.Error("[Error] stack length is wrong")
+    }
 
     stack.Pop()
 
-	if stack.Length() != 2 {
-		t.Error("[Error] stack length is wrong after pop")
-	}
-	
-	if stack.Peek() != 6 {
-		t.Error("[Error] stack Peek is wrong")
-	}
+    if stack.Length() != 2 {
+        t.Error("[Error] stack length is wrong after pop")
+    }
+    
+    if stack.Peek() != 6 {
+        t.Error("[Error] stack Peek is wrong")
+    }
 }