declaractiveNetRequest

Trying to add a parameter to any request going to getshowflow.com.
Original request: getshowflow.com/abcd
Modified request should be getshowflow.com/abcd**?username=siddiqi**

no luck so far, thanks for the help!

[
{
"id": 1,
"priority": 1,
"action": {
"type": "redirect",
"redirect": {
"redirectUrl": "https://www.getshowflow.com/abcd?&user=username",
"permanent": false
}
},
"condition": {
"urlFilter": "https://www.getshowflow.com/*",
"resourceTypes": ["main_frame"]
}
}
]