Restful Webservices in Go

1. Web-Services In Go
U1am Gandhi
@U1amGandhi
h1ps://in.linkedin.com/in/u1am-gandhi-0247aa21
www.synerzip.com

2. Agenda
• REST
• Go Advantage
• Web service example
• TesMng
• Securing using JWT
• HosMng

3. Web-service
• The W3C defines a Web service generally as:
a so%ware system designed to support
interoperable machine-to-machine interac7on
over a network.

4. RESTful Webservice
Client
HTTP
GET
/student/78/scores
{ id: 78, maths : 89, physics:81 }
Server

5. REST
• Introduced by Roy Fielding, 2000
• REpresentaMonal State Transfer
– Use HTTP methods explicitly.
• POST, GET, PUT, DELETE
– Be stateless.
– Expose directory structure-like URIs.
• h1p://www.myservice.org/discussion/topics/{topic}
– Transfer XML, JSON or both

6. Why REST
• Why REST
– Minimize coupling between client and server
– Client becomes resilient to server changes
• Why Not REST
– Secure data should not be sent as URI

7. Stateful design
Client
Web
Service
previousPage++
nextPage = previousPage
return nextPage
GET /book/next_page
JSON response

8. Stateless design
Client
Web
Service
getPage(2)
GET /book/page/2
JSON response

9. Go advantage
• Deployment
– Single binary
– Dependency needs staMc Mme managing
• Performance of go
– Built-in concurrency
• Garbage collecMon

10. Basic web service using FileIO
• The service handles inventory of IPAddresses
• Uses
– net/h1p of for handling h1p request
• h1p.ListenAndServe()
– Handles concurrent requests
– gorrilla/mux for parameterized rouMng
– os and bufio for file handling
• h1ps://github.com/u1amgandhi24/ipalloc

11. Let’s build this webservice….

12. Adding Handlers

13. Handler for Get Request

14. Handler for Post request

15. IPAlloc In AcMon
• ipalloc
• ipalloc service listening on 8123 ….
• curl –XPOST –d
’{“Name”:”dev8”,”IPAddress”:”1.2.3.12”}’
h1p://localhost:8123/ipalloc
• curl –G h1p://localhost:8123/ipalloc/1.2.3.12
{“Name”:”device12”,”IPAddress”:”1.2.3.12”}

16. TesMng
• test and h1ptest
• Write tests in _test.go files
• func TestMain to write setup and tear-down
code
• Test case should start with Test prefix
• go test runs all tests
• go test –cover runs the test and shows
coverage

17. Test An API

18. Securing with JWT.io
• Json web tokens
– JSON Web Token (JWT) is an open standard (RFC 7519)
that defines a compact and self-contained way for securely
transminng informaMon between parMes as a JSON
object.
• Library support
– C, Go, Swip, Scala, .NET, Java, Python, Node.js …...
• Structure of JWT
– base64 encoded header
– base64 encoded payload
– signature of the dot separated header and payload.
• h1ps://github.com/u1amgandhi24/jwtdemo

19. Client Web Service
POST /auth
User=.. Password=…
HTTP 200 OK
{ JWT Token.. }
GET /book/page/2
Auth: JWT Token
HTTP 200 OK
{ Page 2 }
Validate
JWT

20. Generate JWT in go

21. Parse JWT Token in go

22. JWT In AcMon
• jwtdemo
• jwtdemo service listening on 3080 ….
• curl –XPOST –H “AuthenMcaMon :
U3luZXJ6aXAxOlBhc3N3b3JkMQ==” h1ps://localhost:3080/
authenMcate
• "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE0NTU2MTQzOT
Z9.pzRgQSRHwSfUymQPsG-LVaH_2n10g3wxpJltYuiUco0"
• curl –H “AuthenMcaMon :
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE0NTU2MTQzOTZ
9.pzRgQSRHwSfUymQPsG-LVaH_2n10g3wxpJltYuiUco0” h1p://
localhost:3080/book/page/2
{"PageNum":2, "content":"This a sample page”}

23. HosMng
• Heroku
– Signup and install toolbelt
– Create go webapp
– Godep ( dependency manager )
– Push to heroku
• h1ps://mmcgrana.github.io/2012/09/genng-
started-with-go-on-heroku.html

24. Thank You
QuesMons

25. References
• h1p://thenewstack.io/make-a-resxul-json-api-go/
• h1p://www.ibm.com/developerworks/library/ws-
resxul/
• h1ps://scotch.io/tutorials/the-ins-and-outs-of-token-
based-authenMcaMon
• h1p://jwt.io/
• h1p://dghubble.com/blog/posts/json-web-tokens-
and-go/
• h1p://www.tutorialized.com/tutorial/RESTful-Web-
services:-The-basics/40001

26. References
• h1ps://golang.org/pkg/encoding/base64/
#example_Encoding_DecodeString
• h1p://stackoverflow.com/quesMons/
1368014/why-do-we-need-resxul-web-
services
• h1p://di-side.com/di-side/services/web-
soluMons/rest-webservice-symfony/
• h1p://spf13.com/post/soap-vs-rest