Create a HTTPS Server

Generate a certificate

In order to run a HTTPS server, a certificate is necessary. Generating a self-signed certificate with openssl is done by executing this command:

openssl req -x509 -newkey rsa:4096 -sha256 -nodes -keyout key.pem -out cert.pem -subj "/CN=example.com" -days 3650`

The parameters are:

• req Use the certificate request tool
• x509 Creates a self-signed certificate
• newkey rsa:4096 Creates a new key and certificate by using the RSA algorithms with 4096 bit key length
• sha256 Forces the SHA256 hashing algorithms which major browsers consider as secure (at the year 2017)
• nodes Disables the password protection for the private key. Without this parameter, your server had to ask you for the password each time its starts.
• keyout Names the file where to write the key
• out Names the file where to write the certificate
• subj Defines the domain name for which this certificate is valid
• days Fow how many days should this certificate valid? 3650 are approx. 10 years.

Note: A self-signed certificate could be used e.g. for internal projects, debugging, testing, etc. Any browser out there will mention, that this certificate is not safe. In order to avoid this, the certificate must signed by a certification authority. Mostly, this is not available for free. One exception is the “Let’s Encrypt” movement: https://letsencrypt.org

The necessary Go code

You can handle configure TLS for the server with the following code. cert.pem and key.pem are your SSL certificate and key, which where generated with the above command.

package main

import (
    "log"
    "net/http"
)

func main() {
    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        w.Write([]byte("Hello, world!"))
    })

    log.Fatal(http.ListenAndServeTLS(":443","cert.pem","key.pem", nil))
}