Using input variables for runner data_source config


Is it possible to use input variables for the runner configs data_source? When I run waypoint init -update with the below waypoint.hcl file, i get the error There is no variable named "var".

variable "github_token" {
  type = string

runner {
  enabled = true

  data_source "git" {
    url              = ""
    username = "git"
    password = var.github_token

Am I doing something wrong or is it simply not supported? If so, why not?