path.module

• https://developer.hashicorp.com/terraform/language/expressions/references#filesystem-and-workspace-info

  user_data                   = templatefile("${path.module}/assets/your_instance_data.tftpl", {})

path.root
path.cwd

See also

• Terraform workspaces, terraform workspace, [new | select | list | delete | show] -help, Terraform Enterprise (TFE) workspaces
• Terraform Workspaces