Flutter with Firebase Realtime Database, how to displaying the name of the user who made a post

Question

I am creating an application with flutter and Firebase Realtime where I have the functionality that a user can publish an article. What I would like is to list all these articles with the name of the user who published it. But how to display his name knowing that at the database level it is just the ID of the person who made the post that is recorded?. Thanks

Here is the structure of the relative database:

my code from my request with Firebase Realtime:

ref = FirebaseDatabase.instance.reference().child("post").orderByKey();
FirebaseAnimatedList(
  scrollDirection: Axis.vertical,
  shrinkWrap: true,
  query: ref,
  itemBuilder: (BuildContext context, DataSnapshot snapshot,
      Animation<double> animation, int index) {
    return Container(
      padding: EdgeInsets.all(10),
      margin: EdgeInsets.only(bottom: 20),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: <Widget>[
              Row(
                children: <Widget>[
                  Container(
                    width: 50,
                    height: 50,
                    decoration: BoxDecoration(
                        shape: BoxShape.circle,
                        image: DecorationImage(
                            image: NetworkImage(snapshot
                                .value["imagePost"]
                                .toString()),
                            fit: BoxFit.cover)),
                  ),
                  SizedBox(
                    width: 10,
                  ),
                  Column(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: <Widget>[
                      RichText(
                        text: TextSpan(
                          //text: snapshot.value["user_id"].toString(),
                          text: "" +
                              FirebaseDatabase.instance
                                  .reference()
                                  .child('users')
                                  .child(
                                      "${snapshot.value["user_id"].toString()}")
                                  .child('nom')
                                  .toString(),
                          style: TextStyle(
                              color: Colors.grey[900],
                              fontSize: 14,
                              fontWeight: FontWeight.bold,
                              letterSpacing: 1),
                        ),
                      ),
                      SizedBox(
                        height: 3,
                      ),
                      Text(
                        "${timeago.format(DateTime.parse("${DateTime.fromMillisecondsSinceEpoch(snapshot.value['createAt'])}"), locale: 'fr_short')}",
                        style: TextStyle(
                            fontSize: 12, color: Colors.grey),
                      ),
                    ],
                  )
                ],
              ),
            ],
          ),
          SizedBox(
            height: 20,
          ),
          RichText(
            text: TextSpan(
              text: snapshot.value["description"].toString(),
              style: TextStyle(
                  fontSize: 12,
                  color: Colors.grey[800],
                  height: 1.5,
                  letterSpacing: .7),
            ),
          ),
          SizedBox(
            height: 20,
          ),
          snapshot.value["imagePost"].toString() != ''
              ? Container(
                  height: 200,
                  decoration: BoxDecoration(
                    borderRadius: BorderRadius.circular(10),
                    image: DecorationImage(
                        image: NetworkImage(
                            snapshot.value["imagePost"].toString()),
                        fit: BoxFit.cover),
                  ),
                )
              : Container(
                  height: 200,
                  decoration: BoxDecoration(
                    borderRadius: BorderRadius.circular(10),
                    color: kPrimaryColor,
                  ),
                ),
          SizedBox(
            height: 20,
          ),
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: <Widget>[
              makeLikeButton(isActive: false),
              Padding(
                padding: EdgeInsets.only(
                  right: 10,
                ),
              ),
              Row(
                children: <Widget>[
                  makeLike(),
                  SizedBox(
                    width: 5,
                  ),
                  Text(
                    "2.5K",
                    style: TextStyle(
                        fontSize: 10, color: Colors.grey[800]),
                  )
                ],
              ),
            ],
          ),
        ],
      ),
    );
  },
),