How to get/make ginger beer syrup?

I have a sodastream and I want to make my own ginger beer. Not ginger ale, I already know where to get that. I’ve heard that ginger syrup is easy to make. How can I do it?

It’s easy to buy:
https://www.amazon.com/s/?ie=UTF8&keywords=ginger+beer+extract&tag=googhydr-20&index=aps&hvadid=81047977879&hvpos=1o3&hvexid=&hvnetw=g&hvrand=16080198374848360612&hvpone=&hvptwo=&hvqmt=b&hvdev=c&ref=pd_sl_8tndjxof14_b

Chop up some fresh ginger root into a pot filled with three parts sugar to two parts water. Boil for about 20 minutes - watch it like a hawk to make sure it doesn’t boil over. Strain and pour it into a bottle while still hot.