Go ServeMux
last modified April 11, 2024
In this article we show how to do request routing and dispatching in Golang with ServeMux.
$ go version go version go1.22.2 linux/amd64
We use Go version 1.22.2.
HTTP
The Hypertext Transfer Protocol (HTTP) is an application protocol for distributed, collaborative, hypermedia information systems. HTTP protocol is the foundation of data communication for the World Wide Web.
ServeMux
ServeMux is an HTTP request multiplexer. It is used for request routing and dispatching. The request routing is based on URL patterns. Each incoming request's URL is matched against a list of registered patterns. A handler for the pattern that most closely fits the URL is called.
Go NewServeMux
The NewServeMux function allocates and returns a new ServeMux.
package main
import (
"log"
"net/http"
"time"
)
func main() {
mux := http.NewServeMux()
now := time.Now()
mux.HandleFunc("/today", func(rw http.ResponseWriter, _ *http.Request) {
rw.Write([]byte(now.Format(time.ANSIC)))
})
log.Println("Listening...")
http.ListenAndServe(":3000", mux)
}
The example creates an HTTP server which returns the current datetime for the
/today URL pattern.
mux := http.NewServeMux()
A new ServeMux is created.
mux.HandleFunc("/today", func(rw http.ResponseWriter, _ *http.Request) {
rw.Write([]byte(now.Format(time.ANSIC)))
})
A handle to the /today pattern is added with
HandleFunc function.
http.ListenAndServe(":3000", mux)
The created multiplexer is passed to the ListenAndServe function.
Go DefaultServeMux
DefaultServeMux is a just a ServeMux. It is used when we pass
nil to the ListenAndServe method for the second
parameter.
The http.Handle and http.HandleFunc global functions
use the DefaultServeMux multiplexer.
package main
import (
"fmt"
"log"
"net/http"
)
func main() {
http.HandleFunc("/", HelloHandler)
log.Println("Listening...")
log.Fatal(http.ListenAndServe(":3000", nil))
}
func HelloHandler(w http.ResponseWriter, _ *http.Request) {
fmt.Fprintf(w, "Hello there!")
}
The example uses the default multiplexer.
Custom handler
The func (*ServeMux) Handle registers the handler for the given
pattern.
The http.HandlerFunc is an adapter that turns a function, if it has
the right signature, into an http.Handler.
package main
import (
"fmt"
"log"
"net/http"
)
type helloHandler struct {
}
func (h *helloHandler) ServeHTTP(w http.ResponseWriter, _ *http.Request) {
fmt.Fprintf(w, "Hello there!")
}
func main() {
mux := http.NewServeMux()
hello := &helloHandler{}
mux.Handle("/hello", hello)
log.Println("Listening...")
http.ListenAndServe(":3000", mux)
}
In the example, we create a custom handler.
type helloHandler struct {
}
A new type is declared.
func (h *helloHandler) ServeHTTP(w http.ResponseWriter, _ *http.Request) {
fmt.Fprintf(w, "Hello there!")
}
To become a handler, the type must implement the ServeHTTP
function.
hello := &helloHandler{}
mux.Handle("/hello", hello)
We create the handler and pass it to the Handle function.
Source
Go net/http package - reference
In this article we have showed how to do request routing and dispatching in Go with ServeMux.
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