Middlewares in Golang RESTful Web API

Install Libraries

Make sure Git is installed on your machine and in your system’s PATH. Install the packages to your $GOPATH with the go tool from shell:

$ go get -u github.com/gorilla/mux
$ go get -u github.com/gorilla/handlers

Web APIs

In src folder, create new folder named apis. In this folder, create new web folder named demoapi. In demoapi folder, create new apis as below:

API 1

In demoapi folder, create new go file named api1.api.go as below:

package demoapi

import (
	"fmt"
	"net/http"
)

func Demo1API(response http.ResponseWriter, request *http.Request) {
	fmt.Fprint(response, "Demo 1 API")
}

API 2

In demoapi folder, create new go file named api2.api.go as below:

package demoapi

import (
	"fmt"
	"net/http"
)

func Demo2API(response http.ResponseWriter, request *http.Request) {
	fmt.Fprint(response, "Demo 2 API")
}

API 3

In demoapi folder, create new go file named api3.api.go as below:

package demoapi

import (
	"fmt"
	"net/http"
)

func Demo3API(response http.ResponseWriter, request *http.Request) {
	fmt.Fprint(response, "Demo 3 API")
}

Middlewares

In src folder, create new folder named middlewares. In this folder, create new middlewares as below:

Browser Middleware

In middlewares folder, create new folder named browsermiddleware. In browsermiddleware folder, create new go file named browser.middleware.go as below:

package browsermiddleware

import (
	"fmt"
	"net"
	"net/http"
)

func BrowserMiddleware(handler http.Handler) http.Handler {
	return http.HandlerFunc(func(response http.ResponseWriter, request *http.Request) {
		fmt.Println("url: ", request.URL)
		ip, port, _ := net.SplitHostPort(request.RemoteAddr)
		fmt.Println("ip: " + ip)
		fmt.Println("port: " + port)
		handler.ServeHTTP(response, request)
	})
}

Log Middleware

In middlewares folder, create new folder named logmiddleware. In logmiddleware folder, create new go file named log.middleware.go as below:

package logmiddleware

import (
	"fmt"
	"net/http"
	"time"
)

func LogMiddleware(handler http.Handler) http.Handler {
	return http.HandlerFunc(func(response http.ResponseWriter, request *http.Request) {
		today := time.Now()
		fmt.Println("date: " + today.Format("01/02/2006 15:04:05"))
		handler.ServeHTTP(response, request)
	})
}

Structure of Project

Run Application

In src folder, create new file named main.go as below and use go run main.go command to run program:

package main

import (
	"apis/demoapi"
	"fmt"
	"middlewares/browsermiddleware"
	"middlewares/logmiddleware"
	"net/http"

	"github.com/gorilla/mux"
)

func main() {
	router := mux.NewRouter()

	router.Handle("/api/demo/demo1", browsermiddleware.BrowserMiddleware(http.HandlerFunc(demoapi.Demo1API))).Methods("GET")

	router.Handle("/api/demo/demo2", logmiddleware.LogMiddleware(http.HandlerFunc(demoapi.Demo2API))).Methods("GET")

	router.Handle("/api/demo/demo3", logmiddleware.LogMiddleware(browsermiddleware.BrowserMiddleware(http.HandlerFunc(demoapi.Demo3API)))).Methods("GET")

	err := http.ListenAndServe(":3000", router)
	if err != nil {
		fmt.Println(err)
	}
}

Test Web API

Test API 1

Use PostMan Tool test api 1 web api with url: http://localhost:3000/api/demo/demo1

Output in Console

url:  /api/demo/demo1
ip: ::1
port: 38600

Test API 2

Use PostMan Tool test api 2 web api with url: http://localhost:3000/api/demo/demo2

Output in Console

date: 07/14/2019 16:25:39

Test API 3

Use PostMan Tool test api 3 web api with url: http://localhost:3000/api/demo/demo3

Output in Console

date: 07/14/2019 16:27:17
url:  /api/demo/demo3
ip: ::1
port: 38615