添加微信客服SDK (#436)

* 添加微信客服SDK

* polish:优化签名函数

* polish：优化注释内容

* polish:复用已有的Token以及CommonError,移除无用的输出

* polish:复用已有的消息加解密

* fix:修复错误信息被覆盖的问题

* polish:go fmt 文件

work/kf/error.go

@@ -0,0 +1,67 @@
+package kf
+
+import (
+	"reflect"
+	"strings"
+)
+
+// Error 错误
+type Error string
+
+const (
+	// SDKInitFailed 错误码：50001
+	SDKInitFailed Error = "SDK初始化失败"
+	// SDKCacheUnavailable 错误码：50002
+	SDKCacheUnavailable Error = "缓存无效"
+	// SDKUnknownError 错误码：50003
+	SDKUnknownError Error = "未知错误"
+	// SDKInvalidCredential 错误码：40001
+	SDKInvalidCredential Error = "不合法的secret参数"
+	// SDKInvalidCorpID 错误码：40013
+	SDKInvalidCorpID Error = "无效的 CorpID"
+	// SDKAccessTokenInvalid 错误码：40014
+	SDKAccessTokenInvalid Error = "AccessToken 无效"
+	// SDKAccessTokenMissing 错误码：41001
+	SDKAccessTokenMissing Error = "缺少AccessToken参数"
+	// SDKAccessTokenExpired 错误码：42001
+	SDKAccessTokenExpired Error = "AccessToken 已过期"
+	// SDKApiFreqOutOfLimit 错误码：45009
+	SDKApiFreqOutOfLimit Error = "接口请求次数超频"
+	// SDKWeWorkAlready 错误码：95011
+	SDKWeWorkAlready Error = "已在企业微信使用微信客服"
+)
+
+//Error 输出错误信息
+func (r Error) Error() string {
+	return reflect.ValueOf(r).String()
+}
+
+// NewSDKErr 初始化SDK实例错误信息
+func NewSDKErr(code int64, msgList ...string) Error {
+	switch code {
+	case 50001:
+		return SDKInitFailed
+	case 50002:
+		return SDKCacheUnavailable
+	case 40001:
+		return SDKInvalidCredential
+	case 41001:
+		return SDKAccessTokenMissing
+	case 42001:
+		return SDKAccessTokenExpired
+	case 40013:
+		return SDKInvalidCorpID
+	case 40014:
+		return SDKAccessTokenInvalid
+	case 45009:
+		return SDKApiFreqOutOfLimit
+	case 95011:
+		return SDKWeWorkAlready
+	default:
+		//返回未知的自定义错误
+		if len(msgList) > 0 {
+			return Error(strings.Join(msgList, ","))
+		}
+		return SDKUnknownError
+	}
+}