开发语言：golang

环境：已经验证过下载证书的接口，签名的部分是没有问题的

验签失败返回信息：

{"code":"SIGN_ERROR","detail":{"detail":{"issue":"sign not match"},"field":"signature","location":"authorization","sign_information":{"method":"POST","sign_message_length":76,"truncated_sign_message":"POST\n/v3/merchant/media/upload\n1583330550\nFBBD6P84OE7UT4QRTTEBIWAR77S63DON\n\n","url":"/v3/merchant/media/upload"}},"message":"错误的签名，验签失败"}

签名字符串：

请求头信息：

header: map[
  Accept:[application/json] 
  Authorization:[WECHATPAY2-SHA256-RSA2048 mchid="1551027311",nonce_str="FBBD6P84OE7UT4QRTTEBIWAR77S63DON",signature="TShejIcGe92nrXCx1Z9MQRNaipCbY2EvSJX5aB5lMOk+k+ForhpNuQqXC7zAg0AtCHHardwB3LEHDwmASFtsVMkX2j9BYS2dyBFFsKV3Ijr4cjdYyXVVNW0WcigbQmL+l/vENRecAjaR9roCOgdlSbgH0UVZ3b0GvPHxM332Hf3xo2j6bam/WScWnFlq17EugHPk5Tt9VY174KkZa4DmQNkwR1DK2z/OQ8rVnTqFdwJ7p1poRDBIXRZ0mU7eVRwmc8sZqW82l/TPiDdAN7EkAdsvjPAMHlrmOa5c1VgUBmKtZmKudYBpK9mXdUypWFDrDgoOmIzbw6R95p2edcDeXQ==",timestamp="1583330077",serial_no="1FBF8E58E92E1BC0D35B2687B6B61C262196EDCD"] 
  Content-Type:[multipart/form-data;boundary="boundary"] 
  User-Agent:[Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.1 (KHTML, like Gecko) Chrome/14.0.835.163 Safari/535.1]
 ]

请求body前半部分：

请求body后半部分：