How to return user name from vibed session?

[Suliman via Digitalmars-d-learn]

On Thursday, 10 December 2015 at 12:30:51 UTC, Suliman wrote:
> On Thursday, 10 December 2015 at 12:21:40 UTC, Adrian Matoga 
> wrote:
>> On Thursday, 10 December 2015 at 11:36:20 UTC, Suliman wrote:
>>> Vibed have method get for user session 
>>> http://vibed.org/api/vibe.http.session/SessionStore
>>>
>>> I set user name for session like this:
>>> req.session.set("username", "admin");
>>>
>>> But I can't understand how to get user name from it:
>>>
>>> abstract std.variant.VariantN!(20) get(
>>>   string id,
>>>   string name,
>>>   lazy std.variant.VariantN!(20) defaultVal
>>> );
>>>
>>> What does every string here mean? Could anybody to show 
>>> example of usage?
>>
>> I think what you need is Session.get, not SessionStore.get:
>>
>> http://vibed.org/api/vibe.http.session/Session.get
>
> Give me example please

I found example in vibenews:
  writeln("USER Session: ", req.session.get!string("username"));

but I can't understand why I should call it like this, but not 
like
  writeln("USER Session: ", req.session.get("username"));

And it's look like it do not return username, or user name are 
set incorrectly:

                         if(dbuser == "admin") // admin name 
hardcoded
                         {
                            _auth.isAuthorizated = true;
                            req.session.set("username", "admin");
                         }
                         else
                         {
                             
req.session.set(request["username"].to!string, dbuser); //set 
current username in parameter of session name
                             writeln("user name is: ", dbuser);
                         }