Can't define the 'const' constructor because the field 'currentUser' is initialized with a non-constant value

Question

• Can't define the 'const' constructor because the field 'currentUser' is initialized with a non-constant value.
• Can't define a const constructor for a class with non-final fields.
• The argument type 'Stream<QuerySnapshot<Map<String, dynamic>>>' can't be assigned to the parameter type 'Widget Function(BuildContext, AsyncSnapshot<QuerySnapshot<Object?>>)'.
• The argument for the named parameter 'builder' was already specified.
• The body might complete normally, causing 'null' to be returned, but the return type is a potentially non-nullable type.

how to solve this error. appriciate your help on this.

people.dart

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:firebase_auth/firebase_auth.dart';


class People extends StatelessWidget {
  const People({Key? key}) : super(key: key);
  var currentUser = FirebaseAuth.instance.currentUser!.uid;

  void callChatScreen(String name, String uid){

  }

  @override
  Widget build(BuildContext context) {
    return StreamBuilder<QuerySnapshot>(
        builder: FirebaseFirestore.instance
            .collection("users")
        .where('uid',isNotEqualTo: currentUser)
            .snapshots(),
              builder:(BuildContext,AsyncSnapshot<QuerySnapshot>snapshot){
          if(snapshot.hasError){
            return Center(
              child: Text("Something went wrong"),
            );
          }


          if (snapshot.connectionState == ConnectionState.waiting) {
            return Center(
              child: Text("Loading"),
            );
          }

          if (snapshot.hasData) {
            return CustomScrollView(
              slivers: [
                CupertinoSliverNavigationBar(
                  largeTitle: Text("People"),
                ),
                SliverList(
                    delegate: SliverChildListDelegate(
                        snapshot.data!.docs.map((DocumentSnapshot document) {
                          Map<String, dynamic>? data = document.data() as Map<String, dynamic>?;

                          return CupertinoListTile(
                            onTap:()=> callChatScreen(data['name'],data['uid'])
                            title: Text(data!['name']),
                            subtitle: Text(data['status']),
                          );

                        }).toList()))
              ],
            );
          }
          //return Container();
              });
      }
  }