Redirect www to http

I think it's a good idea that the URL line "www.mydomain.xy" is redirected to '

http://mydomain.xy

Still, "www" for many people is associated with a web page and makes clear that this phrase can be punched into an URL line.

But how can I achieve this with grav? - Standard methods seem not to be working, and I could not find any instruction on that.
BTW: My contents are living in httpdocs/grav/

W