fix range of buffer passed to message parser

src/lib.rs

@@ -193,7 +193,7 @@ pub async fn get_message<T: AsyncReadExt + std::marker::Unpin>(
     stream: &mut T,
 ) -> Result<MessageHeader, Error> {
     let buf = get_message_bytes(stream).await?;
-    let msg = MessageHeader::deserialize(&buf)?;
+    let msg = MessageHeader::deserialize(&buf[4..])?;
     Ok(msg)
 }