How to web programming with D2?

[canalpay]

I am trying to write the web framework(but not to write, to gain experience.). 
Maybe the framework can has got a MVC  desing pattern. But first, the D2 is not 
has got for the web library and I am decided write to library for web.

I am writed a function for post and get methods. (I am not tried to functions. 
But I think, they are works.)
POST: https://github.com/canalpay/turna/blob/master/library/post.d
GET  :  https://github.com/canalpay/turna/blob/master/library/get.d

Environment variables are easy to write for the function.
But How to write a cookie and session?
I looked at the codes of tango. However, don't understand.(I'm new to d 
programming language.)

function-local template specialization error

[canalpay]

void main()
{
T input(T)()
{}
 
T input(T : string)()
{}
}

Error message :

isimsiz.d(6): found 'input' when expecting ';' following statement
isimsiz.d(6): found ':' when expecting ')'
isimsiz.d(6): found 'string' when expecting ';' following statement
isimsiz.d(6): found ')' instead of statement
isimsiz.d(8): unrecognized declaration
 
Shouldn't that work?

And

void main()
{
void input(T)()
{}
 
void input(T : string)()
{}
}

Again, Shouldn't that work?

Error message:
isimsiz.d(6): Error: declaration input(T : string) is already defined

there is no problem when the templates are in the global namespace.