Function should be returning a promise of a string but doesn't

I'm trying to upload an image and return it's id with the following code:

export function uploadImage(file: any, location: string, next: any): Promise<string> {
    try {
        if (!file) {
            throw new Error("No Image file");
        }
        const id = location + "/" + utilities.generatePushID();
        const options = {
            resource_type: "raw",
            public_id: id,
        };
        return cloudinary.uploader.upload_stream(options, (error: any, result: any) => {
            if (error) {
                 throw new Error("Couldn't upload");
             }
             return result.public_id;
        }).end(file.buffer);
    } catch (err) {
         return next(InternalError(err));
    }
}

However, whenever I try to call the function, it gives me back an UploadStream object rather than the string that I want. It's as if it immediately returns the uploader, rather than the result of the uploader. Why?

#javascript #node-js #typescript