Yes, GOTA can do that if you want it to:
1. When you choose to edit a file via GOTA the document is sent to the local computer and it is opened for editing (for example by LibreOffice, Word, Excel etc.)
2. The user will then see a bubble saying something like "Click here if you want to lock this document so that other users can not edit it".
3. When the file is saved it is automatically uploaded to Group-Office. Another bubble appears saying something like "Click here if you are finished with editing the document, so that other users also may edit it".
The file lock can also be switched on/off manually in Group-Office, for example if you want to work on a document for several days etc.