code: async function getFileInput(args) {
      if (typeof args.in !== 'string') {
          return null;
      }
      // Let any errors fall through to the runProgram() promise
      return JSON.parse(await txtfile.read(path.resolve(args.in)));
  }
docs: Retrieves the input file to send as
  the body of the request.
  
  @param args
  @returns {Promise<*>}