gorilla/mux

gorilla/mux is a request router for Go web servers. When a web server receives an incoming HTTP request, something has to decide which piece of code should handle it, for example, sending a request to /products to one function and a request to /articles to another. That job is called routing, and mux (the name is short for HTTP request multiplexer) is the piece that does it. Go already ships with a basic router in its standard library, and the README points out that mux deliberately implements the same http.Handler interface so it stays compatible with the standard one. What mux adds is more powerful matching. You can match a request by URL path, host or subdomain, path prefix, scheme, HTTP method, header value, query string value, or even a custom function. Paths can include named variables, optionally constrained by a regular expression, and your handler reads them back through a helper called mux.Vars. The README also describes subrouters, which let you group routes that share common conditions (for example, every URL under a given host or path prefix) so they are only tested when the parent route matches, convenient and also a performance optimisation. Other built-in features include reverse URL building from a registered route, serving static files, serving single-page apps alongside an API, middleware, CORS handling, and graceful server shutdown. You install it with go get -u github.com/gorilla/mux and use it by creating a router with mux.NewRouter and attaching handlers to URL patterns.