Is there some information about how to set-up your own proxy/checksum DB? EDIT: I understand that there are environment variables you can set, but how do I go

Is there some information about how to set-up your own proxy/checksum DB? EDIT: I understand that there are environment variables you can set, but how do I go about deploying my own proxy/checksum server? Is the source code behind https://sum.golang.org/ https://sum.golang.org/ published somewhere?