async function and await keyword not returning any value

Hi,

I am trying to get the SourceID of the document in Async call using await keyword but i am not getting the value.

I am new to this concept, could anyone tell where i am doing mistake. I have added my code in below code snippet

 public async GetListItems(ListTitle: string): Promise {
        debugger;
        let ListCardItemsArray: ListCardListItem[] = [];
        let ListCardListItm: ListCardListItem = null;

        return new Promise(async (resolve, reject) => {
            await sp.web.lists.getByTitle(ListTitle).items.select("*").get().then((results: any) => {
                results.map((result: any) => {
                    let sourceID: string;
                    ListCardListItm = new ListCardListItem();
                    ListCardListItm["Title"] = result.Title;
                    ListCardListItm["Description"] = result.Description;
                    ListCardListItm["DocumentURL"] = result.DocumentURL;
                   //here i am calling my method
                    let sourceID =  this.GetSourceID("");
                    ListCardListItm["SourceID"] = "";
                    ListCardListItm["VisioURL"] = result.VisioURL;
                    ListCardItemsArray.push(ListCardListItm);
                })
                console.log(ListCardItemsArray);
                resolve(ListCardItemsArray);
            }, (error: any) => {
                console.log("Error of GetListItems " + error);
                resolve(error);
            });

        });
    }


 public async GetSourceID(LinkURL: string) {
        let sourceID: string = "";
        try {
            let result = await sp.web.getFileByUrl("https://contosa.sharepoint.com/:u:/r/sites/Sample/SampleLibrary/Sample.vsdx?d=we836259ffe4b4f6c96ca6dd1118e6629&csf=1&web=1&e=B2w69d").select("*").get();
            sourceID = await result.UniqueId;
            console.log(sourceID);
            return sourceID;
        } catch (error) {
            console.log(error);
        }

    }