Using .require for struct types

[Erdem Demir via Digitalmars-d-learn]

import std;

    struct A
    {
        double val;
        bool isBig;
    }

    void main() {
        alias DListOfA = DList!A;
        DListOfA[string] temp;
        A a = {2.0, true};

        DListOfA returnVal = temp.require("a", DListOfA());--> I 
wish I could use ref DListOfA here

        returnVal.insert(a);
        writeln(temp);
    }

On the reference page there is an example with class types only 
(https://dlang.org/spec/hash-map.html) but my type in associative 
array is a DList which is a struct type and that causes I am 
having a copy of my DList after require an operation. And of 
course my insert is happening to the copy and is not affecting to 
the associative array. ,


I wish I could use ref DListOfA returnVal = .... but we can't in 
D.

Can you please suggest alternatives?