Request的Body只能读取一次

环境：net core 6.0

//这里的流还没有被读取过，直接复制一份CanSeek为false的stream 流 ，进行替换
app.Use(async (context, next) =>
{
    // Keep the original stream in a separate
    // variable to restore it later if necessary.
    var stream = context.Request.Body;
    // Optimization: don't buffer the request if
    // there was no stream or if it is rewindable.
    if (stream == Stream.Null || stream.CanSeek)
    {
        await next.Invoke();
        return;
    }
    try
    {
        using (var buffer = new MemoryStream())
        {
            // Copy the request stream to the memory stream.
            await stream.CopyToAsync(buffer);
            // Rewind the memory stream.
            buffer.Position = 0L;
            // Replace the request stream by the memory stream.
            context.Request.Body = buffer;
            // Invoke the rest of the pipeline.
            await next.Invoke();
        }
    }
    finally
    {
        // Restore the original stream.
        context.Request.Body = stream;
    }
});