支持公众号账号迁移，获取openID变化接口 (#370)

* * 公众号菜单管理，set相关函数，返回btn本身，方便以字面量的方式创建多个菜单，更直观，方便管理

* * golangci-lint fix

* * 获取二维码ticket接口没有往上抛接口错误

* * 增加GetOpenID方法，以获取消息的生产用户openID

* * 支持公众号账号迁移，获取openID变化接口

* * bugfix

* * golint fix

* * golint fix

util/util.go

@@ -0,0 +1,41 @@
+package util
+
+//SliceChunk 用于将字符串切片分块
+func SliceChunk(src []string, chunkSize int) (chunks [][]string) {
+	total := len(src)
+	chunks = make([][]string, 0)
+	if chunkSize < 1 {
+		chunkSize = 1
+	}
+	if total == 0 {
+		return
+	}
+
+	chunkNum := total / chunkSize
+	if total%chunkSize != 0 {
+		chunkNum++
+	}
+
+	chunks = make([][]string, chunkNum)
+
+	for i := 0; i < chunkNum; i++ {
+		for j := 0; j < chunkSize; j++ {
+			offset := i*chunkSize + j
+			if offset >= total {
+				return
+			}
+
+			if chunks[i] == nil {
+				actualChunkSize := chunkSize
+				if i == chunkNum-1 && total%chunkSize != 0 {
+					actualChunkSize = total % chunkSize
+				}
+				chunks[i] = make([]string, actualChunkSize)
+			}
+
+			chunks[i][j] = src[offset]
+		}
+	}
+
+	return
+}

util/util_test.go

@@ -0,0 +1,18 @@
+package util
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSliceChunk(t *testing.T) {
+	src1 := []string{"1", "2", "3", "4", "5"}
+	assert.Equal(t, [][]string{{"1", "2"}, {"3", "4"}, {"5"}}, SliceChunk(src1, 2))
+	assert.Equal(t, [][]string{{"1", "2", "3", "4", "5"}}, SliceChunk(src1, 5))
+	assert.Equal(t, [][]string{{"1", "2", "3", "4", "5"}}, SliceChunk(src1, 6))
+	assert.Equal(t, [][]string{{"1"}, {"2"}, {"3"}, {"4"}, {"5"}}, SliceChunk(src1, 1))
+	assert.Equal(t, [][]string{{"1"}, {"2"}, {"3"}, {"4"}, {"5"}}, SliceChunk(src1, 0))
+	assert.Equal(t, [][]string{{"1"}, {"2"}, {"3"}, {"4"}, {"5"}}, SliceChunk(src1, -100))
+	assert.Equal(t, [][]string{}, SliceChunk(nil, 5))
+}