Call a function in a parsed Jint program

I use Jint to parse JS code and call functions in it. As I use a multithreaded environment, I use the program-parsing approach as indicated in the response to this issue: https://github.com/sebastienros/jint/issues/384

So what I have is a Jint.Parser.Ast.Program instance. I can iterate through the IFunctionDeclarations in it and find my functions. But I don't know how to actually call the functions...

Dim parser As New Jint.Parser.JavaScriptParser
Dim program As Jint.Parser.Ast.Program = parser.Parse(code)

For Each func As Jint.Parser.IFunctionDeclaration In program.FunctionDeclarations
    If func.Id.Name = myFunctionName Then
        ' How to call the function?
    End If
Next

I only found a way to execute the whole Program. I assume that I must do that, so that the functions are actually defined in an engine. But still, how can I call a certain function in my script?

Once your program is executed, just use the same method to execute your function. Example is c#

var parser = new Jint.Parser.JavaScriptParser();
// _parserCache is a static ConcurrentDictionary<string, Jint.Parser.Ast.Program>
var program = _parserCache.GetOrAdd(scriptName, key => parser.Parse(code));

foreach (var func in program.FunctionDeclarations)
{
    if (func.Id.Name == myFunctionName)
    {
        var exec = new Engine();
        // The entire program is executed, to define the function
        exec.Execute(program);
        // now you can call your function
        exec.Execute($"{myFunctionName}()");
    }
}