multiple aws providers - HOW?????

ec2.tf

terraform {
  required_version = ">= 0.13"
  required_providers {
    aws = {
      source = "hashicorp/aws",
      version = "~> 3.10"
    }
  }
}
### Resources
resource "aws_instance" "prometheus" {
  ami  = data.aws_ami.default.id
  provider = aws.dev
  instance_type = var.instance_type
  subnet_id     = data.aws_subnet.private.id
  key_name      = "ec2-user"
  vpc_security_group_ids = [
    data.aws_security_group.linux_admin.id
  ]
  iam_instance_profile = "prometheus"
  monitoring           = true
  user_data = data.template_file.userdata.rendered
}

execution errors.md

@  $ tf validate
╷
│ Error: Provider configuration not present
│
│ To work with module.dev.aws_instance.prometheus its original provider configuration at
│ module.dev.provider["registry.terraform.io/hashicorp/aws"].dev is required, but it has been removed. This occurs
│ when a provider configuration is removed while objects created by that provider still exist in the state. Re-add
│ the provider configuration to destroy module.dev.aws_instance.prometheus, after which you can remove the provider
│ configuration again.
╵

stack.tf

terraform {
  required_version = ">= 0.13"
  required_providers {
    aws = {
      source = "hashicorp/aws",
      version = "~> 3.10"
    }
  }
}

###  Providers
provider "aws" {
  region              = "us-east-2"
  alias               = "staging"
}

provider "aws" {
  alias   = "dev"
  region  = "us-west-2"
}

# module
module "dev" {
  source = "./ec2"
  providers = {
    aws = aws.dev
  }
}