function createMutex(doWork) {
  const mutex = {};

  return function(key, payload, callback) {
    if (mutex[key]) {
      mutex[key].push(callback);
    } else {
      mutex[key] = [
        function() {
          delete mutex[key];
        },
        callback
      ];

      doWork(payload, function(error, value) {
        mutex[key].forEach(callback => {
          callback(error, value);
        });
      });
    }
  };
}

module.exports = createMutex;