add erfen in go

animation-simulation/二分查找及其变种/找出第一个大于或小于目标的索引.md

@@ -98,3 +98,27 @@ public static int upperBoundnum(int[] nums,int target,int left, int right) {
 }
 ```
 
+Go Code:
+```go
+func upperBoundnum(nums []int, target, left, right int) int {
+
+	for left <= right {
+
+		mid := left + ((right - left) >> 1)
+		//小于目标值
+		if nums[mid] < target {
+			//看看是不是当前区间的最后一位，如果当前小于，后面一位大于，返回当前值即可
+			if mid == right || nums[mid+1] >= target {
+				return mid
+			} else {
+				left = mid + 1
+			}
+
+		} else if nums[mid] >= target {
+			right = mid - 1
+		}
+	}
+	//没有查询到的情况
+	return -1
+}
+```