code: function set(path, value, opts) {
    if (typeof opts === 'undefined') {
      opts = {};
    }
  
    let env = toUnderscore(path);
    if (!opts.caseSensitive) {
      env = env.toUpperCase();
    }
  
    del(path, opts);
    process.env[env] = stringify(value, opts);
  }
docs: Sets an env key at the path specified. If nested keys are present they will
  be deleted.
  @public
  @param  {string} path Dot separated path.
  @param  {string} value Value to set.
  @param  {object} [opts] Additional options.
  @param  {boolean} [opts.stringify=false] If true the value provided is
  converted to string.
  @param  {boolean} [opts.caseSensitive=false] If true no case conversion is
  performed from the dot path provided to the env key search.
  Eg: 'tesT.kEy' will look for tesT_kEy environment variable instead of TEST_KEY.