Base64OrigLength 计算 base64 数据长度 https://stackoverflow.com/questions/56140620/how-to-get-original-file-size-from-base64-encode-string.

FixUnknownMessage 修复wechaty服务端不能解析的消息，尝试服务端去解析.

NewAsync ...

ParseMiniApp 解析小程序xml.

ParseRecalledID 从 xml 中解析撤回的原始消息id.

DefaultWorkerNum default number of goroutines is twice the number of GOMAXPROCS.

Msg 小程序xml消息体.

RecalledMsg 撤回消息的 xml 结构体.