- 当前 Bug 的表现（可附上截图）

    返回结果：

    {"errorCode":1,"errorMessage":"user code exception caught","stackTrace":"Error: errCode: -501001 resource system error | errMsg: uploadFile:fail MultipartParser.end(): stream ended unexpectedly: state = PART_DATA; at uploadFile api; \n    at new CloudSDKError (/var/user/node_modules/wx-server-sdk/index.js:2679:28)\n    at returnAsCloudSDKError (/var/user/node_modules/wx-server-sdk/index.js:2731:16)\n    at Object.returnAsFinalCloudSDKError (/var/user/node_modules/wx-server-sdk/index.js:2745:13)\n    at Object.\u003canonymous\u003e (/var/user/node_modules/wx-server-sdk/index.js:2213:58)\n    at step (/var/user/node_modules/tslib/tslib.js:133:27)\n    at Object.throw (/var/user/node_modules/tslib/tslib.js:114:57)\n    at rejected (/var/user/node_modules/tslib/tslib.js:105:69)\n    at \u003canonymous\u003e\n    at process._tickCallback (internal/process/next_tick.js:188:7)"}

- 预期表现

    传入了要求的参数【可读流】，调用应该成功

- 复现路径

- 提供一个最简复现 Demo

    提供三种云函数调用case，均无法实现写数据到存储，本地测试创建的可读流没有问题

const cloud = require('wx-server-sdk')

const fs = require('fs')

const streamifier = require('streamifier')

var streamBuffers = require('stream-buffers');

cloud.init()

exports.main = async (event, context) => {

/* --------------------------case0---------------------------------

 var readerStream = new stream.PassThrough();

 readerStream.end(new Buffer('Test data.'));

 ----------------------------------------------------------------------*/

/* --------------------------case1---------------------------------

 let readerStream = streamifier.createReadStream(new Buffer('Test data.'))

 ----------------------------------------------------------------------*/

/* --------------------------case2---------------------------------

 var readerStream = new streamBuffers.ReadableStreamBuffer({

   frequency: 10,      // in milliseconds.

   chunkSize: 2048     // in bytes.

 });

 readerStream.put('Test data.');

 readerStream.stop();

 ----------------------------------------------------------------------*/

return await cloud.uploadFile({

        cloudPath: 'demo.txt',

        fileContent: readerStream

    })

}