官方文档：https://developers.weixin.qq.com/miniprogram/dev/api/network/upload/wx.uploadFile.html

filepath:通过wx.chooseImage获取
formData：采用结构
name:自取
formData: {
          "uploaduser": uploaduser
        },


后端部分：基于python的flask
@app.route('/uploadfiles', methods=['POST'])
def uploadfile():
    file = request.files['file1']  # 获取上传的文件
    formdatas = request.values  # 获取format中的值，取值以   uploaduser = formdatas["uploadyear"] 方式
    filename = file.filename  # 获取文件名
    directory = '/test/test/'
    file_path = os.path.join(directory, filename)
    file.save(file_path)