code: function closeConnection(options) {
    //no options, close/delete all connection references
    if (!options) {
      try {
        mssql.close();
      } catch(err){}
  
      //create list to track items to close
      let closeList = [];
  
      //iterate through each connection
      for (let key in promises) {
        //if there's a close method (connection match), add it to the list
        if (promises[key] && typeof promises[key].close === 'function') closeList.push(promises[key]);
      }
  
      //iterate through list and close each connection
      closeList.forEach((item)=>item.close());
    }
  
    //either a connection promise, or a connection
    if (options._mssqlngKey && typeof options.close === 'function') return options.close();
  
    //match against connection options
    let key = stringify(options || {});
    if (connections[key]) connections[key].close();
    if (promises[key]) promises[key].then((conn)=>conn.close()).catch(()=>{ delete promises[key]; delete connections[key] });
  }
docs: close a specific connection, if no options specified, deletes all connections