public class caseReportGenerator{
    public static void caseReport(){
    
        list<user> u=[select id,name,email,isactive from user where id in (select userorgroupid from groupmember where group.name = 'HR - HR Tech Ops') and isActive=true];
    map<string,integer>userList= new  map<string,integer>();
    map<string,integer>usersInQueue= new  map<string,integer>();
    list<AggregateResult>caseCount=[select owner.name userName,count(id) Total from case group by owner.name ];
for(AggregateResult aggResult : caseCount)
{
  userList.put((String)aggResult.get('userName'), (integer)aggResult.get('total'));
}
    
    for(user uu:u)
    {
       if(userList.containsKey(uu.id))
       {
           
           usersInQueue.put(uu.name,userList.get(uu.name));
       }
    }
    
    string csvHeader = 'User Name,Count \n';

   string mainContent = csvHeader;

for (string  s: usersInQueue.keySet()) {

   
    string recordString = s+','+usersInQueue.get(s) +'\n';
     mainContent += recordString;
system.debug('rrrrrrrr'+recordString );
system.debug('mmmmmmmmmm'+mainContent );
}
Messaging.EmailFileAttachment csvAttcmnt = new Messaging.EmailFileAttachment ();

//Create CSV file using Blob

blob csvBlob = Blob.valueOf (mainContent);

string csvname= 'Case Report.csv';

csvAttcmnt.setFileName (csvname);

csvAttcmnt.setBody (csvBlob);

Messaging.SingleEmailMessage singEmail = new Messaging.SingleEmailMessage ();

String [] toAddresses = new list<string> {'hiteshwar_mani@intuit.com'};

//Set recipient list

singEmail.setToAddresses (toAddresses);

String subject ='Case Reportcsv';

singEmail.setSubject (subject);

singEmail.setPlainTextBody ('Case Report csv');

//Set blob as CSV file attachment

singEmail.setFileAttachments (new Messaging.EmailFileAttachment []{csvAttcmnt});

Messaging.SendEmailResult [] r = Messaging.sendEmail (new Messaging.SingleEmailMessage [] {singEmail});










    }
}

Here I'm geting records into each and every debug statement.but i'm not getting records into csv attachment.please help me 

thanks