Error: already ended, I created a list of pdf paths and tried to merge them in one file, but I'm getting Unhandled promise Error: already ended

Question

I created a list of pdf paths and tried to merge them in one file, but I'm getting Unhandled promise Error: already ended

this is my code, I tried also to await while adding to pdf but didn't like it Is there any way to handle this error?

 listOFPdf.push(docPath.filepath);//list of pdf paths
    const merger = new PDFMerger();
    (async()=>{
      listOFPdf.forEach(file=> { //loop through paths and merge them
      const mergedPdf = await merger.save(file); // save the path
    })
  }) ();// calling the function