Go Language

Writing Custom HTTP Router in Golang

Its this article we will create a simple router to server request in golang server

Golang Community Moderator. Software Engineer - Open Source Enthusiast. Goper Lover

Published · Jun 20 2019

As stated in the title of this article, we are going to build a router (also known as a mux) in Go. 

Now you might be asking why? There are a plethora of great routers out there so why "reinvent the wheel"? As a mentor of mine use to say "to learn how wheels 
work". So without further ado, let's jump in.
. . .
Creating Router
package router

import (
  "fmt"
  "net/http"
)

// Router serves http
type Router struct {
  handlers map[string]func(http.ResponseWriter, *http.Request)
}

// NewRouter creates instance of Router
func NewRouter() *Router {
  router := new(Router)
  router.handlers = make(map[string]func(http.ResponseWriter, *http.Request))
  return router
}

// ServeHTTP is called for every connection
func (s *Router) ServeHTTP(w http.ResponseWriter, r *http.Request) {
  f, ok := s.handlers[key(r.Method, r.URL.Path)]
  if !ok {
    bad(w)
    return
  }
  f(w, r)
}

After implenting the handler lets build our GET, POST handler that will handle our request. You can extend it furter by adding more methods  if required.
// GET sets get handler
func (s *Router) GET(path string, f http.HandlerFunc) {
  s.handlers[key("GET", path)] = f
}

// POST sets post handler
func (s *Router) POST(path string, f http.HandlerFunc) {
   s.handlers[key("POST", path)] = f
}

// DELETE sets delete handler
func (s *Router) DELETE(path string, f http.HandlerFunc) {
  s.handlers[key("DELETE", path)] = f
}

// PUT sets put handler
func (s *Router) PUT(path string, f http.HandlerFunc) {
  s.handlers[key("PUT", path)] = f
}

func key(method, path string) string {
  return fmt.Sprintf("%s:%s", method, path)
}

func bad(w http.ResponseWriter) {
  w.Header().Set("Content-Type", "application/json")
  w.Write([]byte(`{"error":"not found"}`))
}

. . .
Usage
Its time to use our router
package main
import(
    mux "github.com/gufranmirza/go-router"
    "net/http"
    "log"
)

func boo(w http.ResponseWriter, r *http.Request){
    // do something
}

func foo(w http.ResponseWriter, r *http.Request){
    // do something
}

func main() {
	router := mux.NewRouter()
	router.GET("/boo", boo)
	router.POST("/foo", foo)
	log.Fatal(http.ListenAndServe(":8080", router))
}

. . .