code: function readSpecFile(file, options) {
      if (options.verbose > 1) {
          file ? console.error('GET ' + file) : console.error('GET <stdin>');
      }
      if (!file) {
          // standard input
          return readFileStdinAsync();
      } else if (file && file.startsWith('http')) {
          // remote file
          return fetch(file).then(res => {
              if (res.status !== 200) {
                  throw new Error(`Received status code ${res.status}`);
              }
              return res.text();
          })
      } else {
          // local file
          // TODO error handlers?
          return readFileAsync(file, 'utf8');
      }
  }
docs: file can be null, meaning stdin