Saravanan Gnanaguru for Kubernetes Community Days Chennai

Posted on May 4, 2022 • Originally published at dev.to

Develop REST API using Go with API versioning, Basic Auth and Query String

#go #beginners #tutorial #restapi

Table of content

Introduction
Objective
Source Repo
Function main
Get Method
Full Source Code
Go REST API Unit testing
Executing Go Unit Testing
Go Source Build and Run
Real time test
- Localhost method
- Ngrok method
Conclusion

Introduction

We have learnt how to create simple REST API in the previous blog.
We will see the below topics in this blog,
How to,

Add REST API versioning
Create query string parameters
Add basic authentication to REST API
Write Go unit testing for API authentication code
Test the REST API with authentication in real time

Objective

We will be creating REST API that listens on localhost port 1357 and has the API versioning with query string parameter.
Sample URL format we are planning to create, http://localhost:1357/api/v1/PersonId/Id432

Source Repo

Checkout the full source repo here in GitHub

Let us start break the code into blocks,

Function main

Add the below code function main()

Adding API Versioning and Basic authentication

  // Define gin router
  router := gin.Default()

  // Create Sub Router for customized API version and basic auth
  subRouterAuthenticated := router.Group("/api/v1/PersonId", gin.BasicAuth(gin.Accounts{
    "basic_auth_user": "userpass",
  }))

Passing Query String Parameters

  subRouterAuthenticated.GET("/:IdValue", GetMethod)

REST API Listening on Port

  listenPort := "1357"
  // Listen and Server on the LocalHost:Port
  router.Run(":"+listenPort)

Get Method

Define a GetMethod function and add the following code
It fetches and prints the Person IdValue from the query string parameter passed in the API URL

func GetMethod(c *gin.Context) {
  fmt.Println("\n'GetMethod' called")
  IdValue := c.Params.ByName("IdValue")
  message := "GetMethod Called With Param: " + IdValue
  c.JSON(http.StatusOK, message)

  // Print the Request Payload in console
  ReqPayload := make([]byte, 1024)
  ReqPayload, err := c.GetRawData()
  if err != nil {
        fmt.Println(err)
        return
  }
  fmt.Println("Request Payload Data: ", string(ReqPayload))
}

Full Source Code

// Golang REST API with API versioning and Basic Auth
package main

import (
  "fmt"
  "net/http"
  "github.com/gin-gonic/gin"
)

func GetMethod(c *gin.Context) {
  fmt.Println("\n'GetMethod' called")
  IdValue := c.Params.ByName("IdValue")
  message := "GetMethod Called With Param: " + IdValue
  c.JSON(http.StatusOK, message)

  ReqPayload := make([]byte, 1024)
  ReqPayload, err := c.GetRawData()
  if err != nil {
        fmt.Println(err)
        return
  }
  fmt.Println("Request Payload Data: ", string(ReqPayload))
}

func main() {
  router := gin.Default()

  // Create Sub Router for  customised API version
  subRouterAuthenticated := router.Group("/api/v1/PersonId", gin.BasicAuth(gin.Accounts{
    "admin": "adminpass",
  }))

  subRouterAuthenticated.GET("/:IdValue", GetMethod)

  listenPort := "1357"
  // Listen and Server on the LocalHost:Port
  router.Run(":"+listenPort)
}

Go REST API Unit testing

Go testing module can be used for creating unit testing code for Go source
Go Unit testing code looks as below,

// Golang REST API unit testing program
package main

import (
  "testing"
  "net/http"
  "net/http/httptest"
  "fmt"
  "bytes"

  "github.com/gin-gonic/gin"
)
func TestGetMethod(t *testing.T) {
    // Switch to test mode so you don't get such noisy output
    gin.SetMode(gin.TestMode)

    // Create the mock request you'd like to test. Make sure the second argument
    // here is the same as one of the routes you defined in the router setup
    // block!
    body := bytes.NewBuffer([]byte("{\"ApiTest\":\"GetReq\"}"))
    req, err := http.NewRequest("GET", "/api/v1/PersonId/Id456", body)
    if err != nil {
        t.Fatalf("Couldn't create request: %v\n", err)
    }
    req.Header.Set("Content-Type", "application/json")
    req.SetBasicAuth("admin", "adminpass")

    // Setup your router, just like you did in your main function, and
    // register your routes
    router := gin.Default()
    router.GET("/api/v1/PersonId/:IdValue", GetMethod)

    // Create a response recorder so you can inspect the response
    w := httptest.NewRecorder()

    // Perform the request
    router.ServeHTTP(w, req)
    fmt.Println(w.Body)
}

Refer my previous blog section Write go test program to know more about writing go test code

Executing Go Unit Testing

Run the command go test and it shows the below output in console,

'GetMethod' called
Request Payload Data:  {"ApiTest":"GetReq"}
[GIN] 2020/08/03 - 12:26:29 | 200 |         7.2µs |                 | GET      "/api/v1/PersonId/Id456"
"GetMethod Called With Param: Id456"
PASS
ok      apiauth 0.008s

This confirms the REST API code we have created is working fine.

Go Source Build and Run

If we want to test the API in our server, on which the code is created, run the below command

go run apiauth.go

This command invokes the REST API on localhost port 1357 & console shows the below output,

[GIN-debug] [WARNING] Creating an Engine instance with the Logger and Recovery middleware already attached.

[GIN-debug] [WARNING] Running in "debug" mode. Switch to "release" mode in production.
 - using env:   export GIN_MODE=release
 - using code:  gin.SetMode(gin.ReleaseMode)

[GIN-debug] GET    /api/v1/PersonId/:IdValue --> main.GetMethod (4 handlers)
[GIN-debug] Listening and serving HTTP on :1357

Then proceed to test the REST API real-time

Real time test

Localhost method

Run curl with basic authentication user-password

curl -u admin:adminpass -i -X GET http://localhost:1357/api/v1/PersonId/Id456

This will show the output as below in Console

"GetMethod Called With Param: Id456"

In Ubuntu, Access the localhost URL in browser and enter the basic auth username and password when prompted
After entering the credential, the browser should show, GetMethod Called With Param: Id456

Ngrok method

Execute the go run command to start the API, go run apiauth.go
To verify our REST API, we need to expose the localhost of the server to internet
So we can use "ngrok" for this purpose
Download ngrok here
Extract the ngrok executable in some location on your server.
Start ngrok on port 1357(Port defined in go API code) as below,

./ngrok http 1357 and prints the output as follows in console

ngrok by @inconshreveable                                                    (Ctrl+C to quit)

Session Status                online                                                         
Session Expires               7 hours, 12 minutes                                            
Version                       2.3.35                                                         
Region                        United States (us)                                             
Web Interface                 http://127.0.0.1:4040                                          
Forwarding                    http://ca6d2c4cee3e.ngrok.io -> http://localhost:4000          
Forwarding                    https://ca6d2c4cee3e.ngrok.io -> http://localhost:4000

ngrok generates a dynamic URL. For ex: http://ca6d2c4cee3e.ngrok.io
The REST API can be tested by adding the URL in browser address bar,
http://ca6d2c4cee3e.ngrok.io/api/v1/PersonId/Id456
Browser will prompt to enter the authentication details. So enter credentials
After entering the credential, the browser should show,
GetMethod Called With Param: Id456

Conclusion

We have seen the below topics in this blog,

Adding basic authentication to REST API
Go unit testing for API authentication code
Testing the REST API with basic authentication in real time
This article was previously published on my dev community personal profile, re-publishing for the benefit of a wider audience.
Hope this article is helpful to people getting started with kubernetes concepts.

DEV Community