hexo-renderer-swig has been deprecated.
The swig project seems inactive. We recommend migrate to other template engines. (e.g. nunjucks)
Below references may help migrate from swig to nunjucks.
JS Templating: Transitioning from swig to nunjucks hexo-renderer-nunjucks hexo-theme-next: Migrate to Nunjucks #1214 hexo-theme-next: Use nunjucks-compatible syntax & operator #1068 hexo-theme-next: Migrate to Nunjucks #1215
Add support for Swig.
$ npm install hexo-renderer-swig --save