fix(lsp): use readexactly to ensure all bytes are read (#21)

Author: lljbash

clangd_tidy/lsp/rpc.py

@@ -69,5 +69,5 @@ async def recv(self) -> Dict[str, Any]:
                 break
         if header.content_length is None:
             raise ValueError("Missing Content-Length header field")
-        content = await self._in_stream.read(header.content_length)
+        content = await self._in_stream.readexactly(header.content_length)
         return json.loads(content.decode())