上载文件是否总是需要多部分/表单数据，这是真的吗？

I am working on a rest endpoint which should get the request body stream and consume it. I tried to get the body of request (Content-Type as text/csv or application/octet-stream) and read from it using buffer.

reader := r.Body.(io.Reader)
writer := bufio.NewWriter(outputFile) // we write to

for {
    buffer := make([]byte, 4000)
    numBytes, err := reader.Read(buffer)
    if err == io.EOF {
        break
    } else if err != nil {
        return
    }
    if read > 0 {
        writer.Write(buffer[0:numBytes])
    } else {
        break
    }
}
writer.Flush();

Above is my golang code. I got nothing from the request.Body. However, if I use multipart/form-data I can get the data from the parts. Does http always require form-data for uploading??