Note, currently only the activate method from the Web API is supported.
In order to get started with the library, start by 
go get github.com/Cryptolens/cryptolens-golang/cryptolens
Now we can use the library in our code. A working example of the following can be found in the examples/example_activate directory (the repo link: https://github.com/Cryptolens/cryptolens-golang/tree/go_mod) We start by importing the library with: 
import "github.com/Cryptolens/cryptolens-golang/cryptolens"
Now we can activate a license key as follows: 
token := "WyI0NjUiLCJBWTBGTlQwZm9WV0FyVnZzMEV1Mm9LOHJmRDZ1SjF0Vk52WTU0VzB2Il0="
publicKey := "<RSAKeyValue><Modulus>khbyu3/vAEBHi339fTuo2nUaQgSTBj0jvpt5xnLTTF35FLkGI+5Z3wiKfnvQiCLf+5s4r8JB/Uic/i6/iNjPMILlFeE0N6XZ+2pkgwRkfMOcx6eoewypTPUoPpzuAINJxJRpHym3V6ZJZ1UfYvzRcQBD/lBeAYrvhpCwukQMkGushKsOS6U+d+2C9ZNeP+U+uwuv/xu8YBCBAgGb8YdNojcGzM4SbCtwvJ0fuOfmCWZvUoiumfE4x7rAhp1pa9OEbUe0a5HL+1v7+JLBgkNZ7Z2biiHaM6za7GjHCXU8rojatEQER+MpgDuQV3ZPx8RKRdiJgPnz9ApBHFYDHLDzDw==</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>"

licenseKey, err := cryptolens.KeyActivate(token, cryptolens.KeyActivateArguments{
	ProductId:   3646,
	Key:         "MPDWY-PQAOW-FKSCH-SGAAU",
	MachineCode: "289jf2afs3",
})
if err != nil || !licenseKey.HasValidSignature(publicKey) {
	fmt.Println("License key activation failed!")
	return
}
In order to use the code above with your account on cryptolens.io you need to change the constants as follows:
  1. The token need to be changed to a valid access token for your account. Access tokens can be created at https://app.cryptolens.io/User/AccessToken/. In order to be able to use the KeyActivate() function the token needs to have the Activate scope.
  2. The correct value for publicKey for your account can be found when logged in on Cryptolens.io from the menu in the top-right corner (“Hello !”) and then Security Settings. Copy paste the value from the Public key field.
  3. The ProductId can be found at the page for the corresponding product at https://app.cryptolens.io/Product.
  4. The Key is the license key string, and would in most cases be entered by the user of the application in some application dependent manner.
  5. The MachineCode is an optional argument allowing you to provide an identifier for which device the application is running on, or something with a similar purpuse.
Finally, additional properties of the license key can be checked if desired: 
fmt.Printf("License key for product with id: %d\n", licenseKey.ProductId)

if time.Now().After(licenseKey.Expires) {
	fmt.Println("License key has expired")
	return
}

if licenseKey.F1 {
	fmt.Println("Welcome! Pro version enabled!")
} else {
	fmt.Println("Welcome!")
}

​
Examples

package main

import (
	"fmt"
	"github.com/Cryptolens/cryptolens-golang/cryptolens"
	"time"
)

func main() {
	token := "WyI0NjUiLCJBWTBGTlQwZm9WV0FyVnZzMEV1Mm9LOHJmRDZ1SjF0Vk52WTU0VzB2Il0="
	publicKey := "<RSAKeyValue><Modulus>khbyu3/vAEBHi339fTuo2nUaQgSTBj0jvpt5xnLTTF35FLkGI+5Z3wiKfnvQiCLf+5s4r8JB/Uic/i6/iNjPMILlFeE0N6XZ+2pkgwRkfMOcx6eoewypTPUoPpzuAINJxJRpHym3V6ZJZ1UfYvzRcQBD/lBeAYrvhpCwukQMkGushKsOS6U+d+2C9ZNeP+U+uwuv/xu8YBCBAgGb8YdNojcGzM4SbCtwvJ0fuOfmCWZvUoiumfE4x7rAhp1pa9OEbUe0a5HL+1v7+JLBgkNZ7Z2biiHaM6za7GjHCXU8rojatEQER+MpgDuQV3ZPx8RKRdiJgPnz9ApBHFYDHLDzDw==</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>"

	licenseKey, err := cryptolens.KeyActivate(token, cryptolens.KeyActivateArguments{
		ProductId:   3646,
		Key:         "MPDWY-PQAOW-FKSCH-SGAAU",
		MachineCode: "289jf2afs3",
	})
	if err != nil || !licenseKey.HasValidSignature(publicKey) {
		fmt.Println("License key activation failed!")
		return
	}

	fmt.Printf("License key for product with id: %d\n", licenseKey.ProductId)

	if time.Now().After(licenseKey.Expires) {
		fmt.Println("License key has expired")
		return
	}

	if licenseKey.F1 {
		fmt.Println("Welcome! Pro version enabled!")
	} else {
		fmt.Println("Welcome!")
	}
}