添加（0189.轮转数组.md）：增加go版本

Author: xuerbujia

problems/0189.旋转数组.md

@@ -124,6 +124,19 @@ class Solution:
 ## Go
 
 ```go
+func rotate(nums []int, k int)  {
+    l:=len(nums)
+    index:=l-k%l
+    reverse(nums)
+    reverse(nums[:l-index])
+    reverse(nums[l-index:])
+}
+func reverse(nums []int){
+    l:=len(nums)
+    for i:=0;i<l/2;i++{
+        nums[i],nums[l-1-i]=nums[l-1-i],nums[i]
+    }
+}
 ```
 
 ## JavaScript