GCP Terraform file provisioner not able to connect to VM

Question

I generated public and private key with the below command from terraofrm machine from where I am executing terraform code. ssh-keygen -t rsa -f ~/terraform_projects/vm-module/gcloud_instance1 -C user1 gcloud_instance - private key gcloud_instance.pub - public key

Terraform code.

variable "user" {
  description = "user for ssh"
  type        = string
  default     = "user1"
}

variable "privatekey_path" {
  description = "privatekey_path"
  type        = string
  default     = "~/terraform_projects/vm-module/gcloud_instance"
}

variable "publickey_path" {
  description = "publickey_path"
  type        = string
  default     = "~/terraform_projects/vm-module/gcloud_instance.pub"
}


resource "google_compute_instance" "vm" {
  ....
  ....
  metadata = {
    ssh-keys = "${var.user}:${file("${var.publickey}")}"
  }

}

resource "null_resource" "cluster" {
  provisioner "file" {
    source      = "${path.module}/../scripts"
    destination = "/home/${var.user}/"
  }

  connection {
    host = google_compute_instance.vm.network_interface.0.access_config.0.nat_ip
    type = "ssh"
    user = "${var.user}"
    private_key = file("${var.privatekey_path}")
    timeout     = "2m"
  }
}

I have added public key to the vm machine from the metadata . Verified from console public key added successfully.

I am able to login to vm from terraform machine using ssh -i gcloud_instance [email protected] I ip address in the error is correct ip of the vm.

Getting below error while running the null_resource. If I dont add timeout property it takes 5 mins , and then fails with same error. I tried many things but didnt work . Not able to find where is the issue , can someone please help.

Error

module.virtual_machine.null_resource.cluster: Creating...
module.virtual_machine.null_resource.cluster: Provisioning with 'file'...
module.virtual_machine.null_resource.cluster: Still creating... [10s elapsed]
module.virtual_machine.null_resource.cluster: Still creating... [20s elapsed]
module.virtual_machine.null_resource.cluster: Still creating... [30s elapsed]
module.virtual_machine.null_resource.cluster: Still creating... [40s elapsed]
module.virtual_machine.null_resource.cluster: Still creating... [50s elapsed]
module.virtual_machine.null_resource.cluster: Still creating... [1m0s elapsed]
module.virtual_machine.null_resource.cluster: Still creating... [1m10s elapsed]
module.virtual_machine.null_resource.cluster: Still creating... [1m20s elapsed]
module.virtual_machine.null_resource.cluster: Still creating... [1m30s elapsed]
module.virtual_machine.null_resource.cluster: Still creating... [1m40s elapsed]
module.virtual_machine.null_resource.cluster: Still creating... [1m50s elapsed]
module.virtual_machine.null_resource.cluster: Still creating... [2m0s elapsed]
╷
│ Error: file provisioner error
│ 
│   with module.virtual_machine.null_resource.cluster,
│   on compute-vm/main.tf line 152, in resource "null_resource" "cluster":
│  152:   provisioner "file" {
│ 
│ timeout - last error: SSH authentication failed ([email protected]:22): ssh: handshake failed: ssh:
│ unable to authenticate, attempted methods [none publickey], no supported methods remain
╵