How to play Go Lang with HTTP

Writing Go Lang HTTP/1.1 & HTTP/2 client and server

7 min readMay 5, 2019

Introduction

In this article, we will implement HTTP client and server with both HTTP/1.1 and HTTP/2 protocols; and with Go programming language.

The Go Programming Language

Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.

golang.org

What is HTTP/2

HTTP/2 is the second major version of the application protocol, which was officially standardized in response to Google’s HTTP-compatible SPDY protocol. Following articles explain everything about HTTP/2 clearly.

Introduction to HTTP/2 | Web Fundamentals | Google Developers

HTTP/2 (or h2) is a binary protocol that brings push, multiplexing streams and frame control to the web.

developers.google.com

HTTP/2 Frequently Asked Questions

These are Frequently Asked Questions about HTTP/2.

http2.github.io

Prerequisites

Before starting, you have to setup your machine with Go Lang. Please refer Go Getting Started Guide.

Once you have successfully installed Go, execute go version command to ensure it works. This should display the Go version you installed.

NOTE: All the Go codes in this article are tested and compatible with Go version 1.11.5

HTTP/1.1 Server

The following code represents how to start a simple HTTP/1.1 server in Go. Here, we have implemented a Go echo server, which echoes back the requests.

The main function starts the HTTP(S) service on the port 9191, with the path hello/sayHello. The echoPayload handler function is responsible for the echo logic, which reads the incoming payload and replies with the same payload implementation. You can modify the response by updating the echoPayload handler as you wish.

Since we are starting an HTTP(S) service here, we have to provide a server certificate and a server key. So, both of them are saved inside a directory called cert as server.crt and server.key.

If interested to learn more on the SSL certificates, the following article clearly explains how to work with SSL certificates, private keys, and CSRs.

OpenSSL Essentials: Working with SSL Certificates, Private Keys and CSRs | DigitalOcean

OpenSSL is a versatile command line tool that can be used for a large variety of tasks related to Public Key…

www.digitalocean.com

A sample self-signed certificate and a key file can be found below.

./cert/server.crt

./cert/server.key

Let’s see how to start and test the service after configuring all of the above.

Run the service with the command below:

$ go run http_server.go

You can expect the following output:

Go Backend: { HTTPVersion = 1 }; serving on https://localhost:9191/hello/sayHello

Invoke the service with an HTTP/1.1 POST request with a small text payload (insecure mode and secure mode):

$ curl -k -v https://localhost:9191/hello/sayHello -d "Hello Go!"$ curl -v --cacert ./cert/server.crt https://localhost:9191/hello/sayHello -d "Hello Go!"

Following is the result you get for the above curl command. The first part of the result has details on TLS handshake with the server and client. The next part of the result has the details on HTTP/1.1 request and HTTP/1.1 response. Finally, it has Hello Go! text which received via the response.

*   Trying 127.0.0.1...
* Connected to localhost (127.0.0.1) port 9191 (#0)
* ALPN, offering http/1.1
* Cipher selection: ALL:!EXPORT:!EXPORT40:!EXPORT56:!aNULL:!LOW:!RC4:@STRENGTH
* successfully set certificate verify locations:
*   CAfile: /etc/ssl/certs/ca-certificates.crt
  CApath: none
* TLSv1.2 (OUT), TLS header, Certificate Status (22):
* TLSv1.2 (OUT), TLS handshake, Client hello (1):
* TLSv1.2 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (IN), TLS handshake, Server key exchange (12):
* TLSv1.2 (IN), TLS handshake, Server finished (14):
* TLSv1.2 (OUT), TLS handshake, Client key exchange (16):
* TLSv1.2 (OUT), TLS change cipher, Client hello (1):
* TLSv1.2 (OUT), TLS handshake, Finished (20):
* TLSv1.2 (IN), TLS change cipher, Client hello (1):
* TLSv1.2 (IN), TLS handshake, Finished (20):
* SSL connection using TLSv1.2 / ECDHE-RSA-AES128-GCM-SHA256
* ALPN, server accepted to use http/1.1
* Server certificate:
*        subject: C=LK; ST=Western; L=Colombo; O=LDCLAKMAL; OU=Engineering; CN=Chanaka Lakmal; emailAddress=ldclakmal@gmail.com
*        start date: Apr 20 03:03:58 2019 GMT
*        expire date: Apr 19 03:03:58 2020 GMT
*        issuer: C=LK; ST=Western; L=Colombo; O=LDCLAKMAL; OU=Engineering; CN=Chanaka Lakmal; emailAddress=ldclakmal@gmail.com
*        SSL certificate verify result: self signed certificate (18), continuing anyway.
> POST /hello/sayHello HTTP/1.1
> Host: localhost:9191
> User-Agent: curl/7.46.0
> Accept: */*
> Content-Length: 9
> Content-Type: application/x-www-form-urlencoded
> 
* upload completely sent off: 9 out of 9 bytes
< HTTP/1.1 200 OK
< Date: Sat, 20 Apr 2019 06:56:19 GMT
< Content-Length: 10
< Content-Type: text/plain; charset=utf-8
< 
Hello Go!
* Connection #0 to host localhost left intact

HTTP/1.1 Client

The following code represents how to start a simple HTTP/1.1 client in Go. Here, the Go client sends an HTTP(S) POST request to https://localhost:9191/hello/sayHello with the text payload of “Hello Go!”.

Since we are starting an HTTP(S) service here also, we have to provide a server certificate and a server key. So, both of them are saved inside a directory called cert as server.crt and server.key. More details on SSL configurations are discussed under the previous section (HTTP/1.1 Server).

Let’s see how to start and test the service after configuring all of the above.

In order to run the client, we need to start the server before. Therefore, run the server by referring to the previous section (HTTP/1.1 Server), or start any HTTP(S) server on the port 9191 and the path /hello/sayHello.

$ go run http_client.go

You can expect the following output:

Got response 200: HTTP/1.1 Hello Go!

This client simply demonstrates the behavior of the curl command below:

$ curl -v --cacert ./cert/server.crt https://localhost:9191/hello/sayHello -d "Hello Go!"

The next section describes how to implement an HTTP/2 server and HTTP/2 client with Go. Following two segments are quite the same as the previous sections, but the HTTP version is different.

HTTP/2 Server

The following code represents how to start a simple HTTP/2 server in Go. Here also, we have implemented a Go echo server, which echoes back the requests.

Let’s see how to start and test the service after configuring all of the above.

Run the service with the command below:

$ go run http2_server.go

You can expect the following output:

Go Backend: { HTTPVersion = 2 }; serving on https://localhost:9191/hello/sayHello

Now, we have successfully started the HTTP/2 server. It can be invoked with either HTTP/1.1 requests or HTTP/2 requests. The HTTP/2 server supports both according to the specification.

Invoke the service with an HTTP/1.1 POST request with a small text payload (insecure mode and secure mode):

$ curl -k -v https://localhost:9191/hello/sayHello -d "Hello Go!"$ curl -v --cacert ./cert/server.crt https://localhost:9191/hello/sayHello -d "Hello Go!"

Now, invoke the service with an HTTP/2 POST request with a small text payload (insecure mode and secure mode):

To have curl commands with HTTP/2 support, we use special flag, which is --http2. Refer the below guide to activate it.

Curl With HTTP2 Support

Installing HTTP2 support with the curl command

serversforhackers.com

$ curl -k -v --http2 https://localhost:9191/hello/sayHello -d "Hello Go!"$ curl -v --http2 --cacert ./cert/server.crt https://localhost:9191/hello/sayHello -d "Hello Go!"

Following is the result you get for the above HTTP/2 curl commands. The first part of the result has details on TLS handshake with the server and client. The next part of the result has the details on HTTP/2 request and HTTP/2 response. Finally, it has Hello Go! text which received via the response.

*   Trying 127.0.0.1...
* Connected to localhost (127.0.0.1) port 9191 (#0)
* ALPN, offering h2
* ALPN, offering http/1.1
* Cipher selection: ALL:!EXPORT:!EXPORT40:!EXPORT56:!aNULL:!LOW:!RC4:@STRENGTH
* successfully set certificate verify locations:
*   CAfile: src/hello/cert/server.crt
  CApath: none
* TLSv1.2 (OUT), TLS header, Certificate Status (22):
* TLSv1.2 (OUT), TLS handshake, Client hello (1):
* TLSv1.2 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (IN), TLS handshake, Server key exchange (12):
* TLSv1.2 (IN), TLS handshake, Server finished (14):
* TLSv1.2 (OUT), TLS handshake, Client key exchange (16):
* TLSv1.2 (OUT), TLS change cipher, Client hello (1):
* TLSv1.2 (OUT), TLS handshake, Finished (20):
* TLSv1.2 (IN), TLS change cipher, Client hello (1):
* TLSv1.2 (IN), TLS handshake, Finished (20):
* SSL connection using TLSv1.2 / ECDHE-RSA-AES128-GCM-SHA256
* ALPN, server accepted to use h2
* Server certificate:
*        subject: C=LK; ST=Western; L=Colombo; O=LDCLAKMAL; OU=Engineering; CN=localhost; emailAddress=ldclakmal@gmail.com
*        start date: Apr 20 05:27:33 2019 GMT
*        expire date: Apr 19 05:27:33 2020 GMT
*        common name: localhost (matched)
*        issuer: C=LK; ST=Western; L=Colombo; O=LDCLAKMAL; OU=Engineering; CN=localhost; emailAddress=ldclakmal@gmail.com
*        SSL certificate verify ok.
* Using HTTP2, server supports multi-use
* Connection state changed (HTTP/2 confirmed)
* TCP_NODELAY set
* Copying HTTP/2 data in stream buffer to connection buffer after upgrade: len=0
* Using Stream ID: 1 (easy handle 0x10ddf20)
> POST /hello/sayHello HTTP/1.1
> Host: localhost:9191
> User-Agent: curl/7.46.0
> Accept: */*
> Content-Length: 9
> Content-Type: application/x-www-form-urlencoded
> 
* We are completely uploaded and fine
< HTTP/2.0 200
< content-type:text/plain; charset=utf-8
< content-length:10
< date:Sat, 20 Apr 2019 06:54:50 GMT
< 
Hello Go!
* Connection #0 to host localhost left intact

HTTP/2 Client

The following code represents how to start a simple HTTP/2 client in Go. Here, the Go client sends an HTTP(S) POST request to https://localhost:9191/hello/sayHello with the text payload of “Hello Go!”.

Let’s see how to start and test the service after configuring all of the above.

In order to run the client, we need to start the server before. Therefore, run the server by referring to the previous section (HTTP/2 Server), or start any HTTP(S) server on the port 9191 and the path /hello/sayHello.

$ go run http2_client.go

You can expect the following output:

Got response 200: HTTP/2 Hello Go!

This client simply demonstrates the behavior of the curl command below:

$ curl -v --http2 --cacert ./cert/server.crt https://localhost:9191/hello/sayHello -d "Hello Go!"

You are done. Playing Go Lang with HTTP is simple as that!

Happy coding with Go !

References

RFC 7540 - Hypertext Transfer Protocol Version 2 (HTTP/2)

Internet Engineering Task Force (IETF) M. Belshe Request for Comments: 7540 BitGo Category: Standards Track R. Peon…

tools.ietf.org

Package http2

Package http2 implements the HTTP/2 protocol.

godoc.org

HTTP/2 Adventure in the Go World

Some Thoughts of a Software Developer

posener.github.io

How to play Go Lang with HTTP

Writing Go Lang HTTP/1.1 & HTTP/2 client and server

Introduction

The Go Programming Language

Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.

What is HTTP/2

Introduction to HTTP/2 | Web Fundamentals | Google Developers

HTTP/2 (or h2) is a binary protocol that brings push, multiplexing streams and frame control to the web.

HTTP/2 Frequently Asked Questions

These are Frequently Asked Questions about HTTP/2.

Prerequisites

HTTP/1.1 Server

OpenSSL Essentials: Working with SSL Certificates, Private Keys and CSRs | DigitalOcean

OpenSSL is a versatile command line tool that can be used for a large variety of tasks related to Public Key…

HTTP/1.1 Client

HTTP/2 Server

Curl With HTTP2 Support

Installing HTTP2 support with the curl command

HTTP/2 Client

References

RFC 7540 - Hypertext Transfer Protocol Version 2 (HTTP/2)

Internet Engineering Task Force (IETF) M. Belshe Request for Comments: 7540 BitGo Category: Standards Track R. Peon…

Package http2

Package http2 implements the HTTP/2 protocol.

HTTP/2 Adventure in the Go World

Some Thoughts of a Software Developer

Written by Chanaka Lakmal