installScript: use channel server to fetch latest stable k3s version

Makefile

@@ -10,15 +10,12 @@ ifeq ($(GIT_TAG),)
 GIT_TAG   := $(shell git describe --always)
 endif
 
-# get latest k3s version: grep the tag JSON field, extract the tag and replace + with - (difference between git and dockerhub tags)
-ifneq (${GITHUB_API_TOKEN},)
-K3S_TAG		:= $(shell curl --silent -H "Authorization: token:  ${GITHUB_API_TOKEN}" "https://api.github.com/repos/rancher/k3s/releases/latest" | grep '"tag_name":' | sed -E 's/.*"([^"]+)".*/\1/' | sed -E 's/\+/\-/')
-else
-K3S_TAG		:= $(shell curl --silent "https://api.github.com/repos/rancher/k3s/releases/latest" | grep '"tag_name":' | sed -E 's/.*"([^"]+)".*/\1/' | sed -E 's/\+/\-/')
-endif
+# get latest k3s version: grep the tag and replace + with - (difference between git and dockerhub tags)
+K3S_TAG		:= $(shell curl --silent "https://update.k3s.io/v1-release/channels/stable" | egrep -o '/v[^ ]+"' | sed -E 's/\/|\"//g' | sed -E 's/\+/\-/')
+
 ifeq ($(K3S_TAG),)
 $(warning K3S_TAG undefined: couldn't get latest k3s image tag!)
-$(warning Output of curl: $(shell curl --silent "https://api.github.com/repos/rancher/k3s/releases/latest"))
+$(warning Output of curl: $(shell curl --silent "curl --silent "https://update.k3s.io/v1-release/channels/stable""))
 $(error exiting)
 endif