Why 'terraform import' did not read my configuration?

I'm building a Terraform plugin/provider using Go. I have the following in my schema (link):

Importer: &schema.ResourceImporter{
  State: resourceKubernetesClusterNodePoolImport,
}

And this is the function (link):

func resourceKubernetesClusterNodePoolImport(d *schema.ResourceData, m interface{}) ([]*schema.ResourceData, error) {
	apiClient := m.(*civogo.Client)

	clusterID, nodePoolID, err := utils.ResourceCommonParseID(d.Id())
	if err != nil {
		return nil, err
	}

	log.Printf("[INFO] retriving the node pool %s", nodePoolID)
	resp, err := apiClient.GetKubernetesCluster(clusterID)
	if err != nil {
		if resp != nil {
			return nil, err
		}
	}

	d.Set("cluster_id", resp.ID)
	for _, v := range resp.Pools {
		if v.ID == nodePoolID {
			d.Set("num_target_nodes", v.Count)
			d.Set("target_nodes_size", v.Size)
		}
	}

	return []*schema.ResourceData{d}, nil
}

When I added these debug lines at the top of function above, the results (reg and ok) were empty and false:

reg, ok := d.GetOk("region")
log.Printf("resourceKubernetesClusterNodePoolImport reg %+v\n", reg)
log.Println("resourceKubernetesClusterNodePoolImport ok", ok)
log.Println("resourceKubernetesClusterNodePoolImport d.Get()", d.Get("region"))
if !ok {
	return nil, fmt.Errorf("[ERR] Please provide a region in your import configuration")
}

Traces:

$ echo $TF_LOG
INFO
$ tf import civo_kubernetes_node_pool.my_pool 1b272dc1-836c-4ea7-8f20-4569f20ddbdd:d0c22622-54b3-41c2-9eae-24591737d5ad
2021-08-12T11:22:30.552+0800 [INFO]  Terraform version: 1.0.3
2021-08-12T11:22:30.552+0800 [INFO]  Go runtime version: go1.16.4
2021-08-12T11:22:30.552+0800 [INFO]  CLI args: []string{"/usr/local/bin/terraform", "import", "civo_kubernetes_node_pool.my_pool", "1b272dc1-836c-4ea7-8f20-4569f20ddbdd:d0c22622-54b3-41c2-9eae-24591737d5ad"}
2021-08-12T11:22:30.552+0800 [INFO]  Loading CLI configuration from /Users/zulh/.terraformrc
2021-08-12T11:22:30.553+0800 [INFO]  CLI command args: []string{"import", "civo_kubernetes_node_pool.my_pool", "1b272dc1-836c-4ea7-8f20-4569f20ddbdd:d0c22622-54b3-41c2-9eae-24591737d5ad"}
2021-08-12T11:22:30.629+0800 [INFO]  Failed to read plugin lock file .terraform/plugins/darwin_amd64/lock.json: open .terraform/plugins/darwin_amd64/lock.json: no such file or directory
2021-08-12T11:22:30.631+0800 [INFO]  provider: configuring client automatic mTLS
2021-08-12T11:22:31.284+0800 [INFO]  provider.terraform-provider-civo_v99.0.0: configuring server automatic mTLS: timestamp=2021-08-12T11:22:31.283+0800
2021-08-12T11:22:31.358+0800 [INFO]  provider: configuring client automatic mTLS
2021-08-12T11:22:31.404+0800 [INFO]  provider.terraform-provider-civo_v99.0.0: configuring server automatic mTLS: timestamp=2021-08-12T11:22:31.404+0800
2021-08-12T11:22:31.478+0800 [WARN]  ValidateProviderConfig from "provider[\"registry.terraform.io/civo/civo\"]" changed the config value, but that value is unused
civo_kubernetes_node_pool.my_pool: Importing from ID "1b272dc1-836c-4ea7-8f20-4569f20ddbdd:d0c22622-54b3-41c2-9eae-24591737d5ad"...
2021-08-12T11:22:31.479+0800 [INFO]  provider.terraform-provider-civo_v99.0.0: 2021/08/12 11:22:31 resourceKubernetesClusterNodePoolImport reg: timestamp=2021-08-12T11:22:31.479+0800      <-- this line
2021-08-12T11:22:31.479+0800 [INFO]  provider.terraform-provider-civo_v99.0.0: 2021/08/12 11:22:31 resourceKubernetesClusterNodePoolImport ok false: timestamp=2021-08-12T11:22:31.479+0800 <-- this line
2021-08-12T11:22:31.479+0800 [INFO]  provider.terraform-provider-civo_v99.0.0: 2021/08/12 11:22:31 resourceKubernetesClusterNodePoolImport d.Get(): timestamp=2021-08-12T11:22:31.479+0800  <-- this line
╷
│ Error: [ERR] Please provide a region in your import configuration
│
│
╵

The problem is, I have added the region in my Terraform configuration main.tf file (and saved it) before I run the tf import command above. Here is my main.tf file:

resource "civo_kubernetes_cluster" "my_cluster" {
    name = "my-cluster"
}

resource "civo_kubernetes_node_pool" "my_pool" {
    region = "LON1" <-- this line
}

Why my Terraform plugin/provider sees the region as empty?

From my understanding, Terraform will first read the configuration file before running the import logic. Am I wrong? Did I miss something here?

For the sake of completeness, I'm using Terraform v1.0.3 and this is my provider.tf file...

terraform {
  required_providers {
    civo = {
      source  = "civo/civo"
      version = "99.0.0"
    }
  }
}

provider "civo" {
    token = “my-api-key-here”
}

...where 99.0.0 is the version that I built for my testing only. The latest/prod version for this provider is 0.10.9 when I posted this question.

Importer.State function does not have access to existing config, it is provided an empty resource state with id - see code.

As a workaround you can allow passing region to import command through underscore (or any symbol that does not conflict with symbols in ids or region names), like so:

terraform import civo_kubernetes_node_pool.my_pool <poolid>_<region>

And handle this in you importer function:

func resourceKubernetesClusterNodePoolImport(d *schema.ResourceData, m interface{}) ([]*schema.ResourceData, error) {
    apiClient := m.(*civogo.Client)

    // extract id and region from provided string
    parts := strings.Split(d.Id(), "_")
	if len(parts) != 2 {
		return nil, errors.New("To import a pool, use the format {pool_id}_{region}")
	}

    poolId := parts[0]
	region := parts[1]

    // Set new ID for resource
    d.SetId(poolId)

    // Set region
    d.Set("region", region)

    // Do the rest of the import

    ...
}