code: function getConnection(options) {
    debug('getConnection','start',options);
  
    let key = null;
    let promise = null;
    try {
      //clone options
      options = clone(options);
  
      //serialize the options as a key for pools
      key = stringify(options || {});
  
      //if there's already a promise for the given connection, return it
      if (promises[key]) return promises[key];
  
      //create a new promise for the given connection options
      promise = promises[key] = createConnectionPromise(key, options);
  
      debug('getConnection','success')
      return promise;
    } catch(err) {
      debug('getConnection','error',err);
      return Promise.reject(err);
    }
  }
docs: gets/uses a pooled connection against the options specified