使用子网创建ec2实例时出现不支持的配置错误

Question

我正在学习terraform并尝试创建一个EC2实例，但运行此错误：

  

启动源实例时出错：不支持：当前不支持请求的配置。请查看文档以获取支持的配置。

我把它剥离到一个可重复性最小的例子：

provider "aws" {
  region = "eu-central-1"
}

resource "aws_vpc" "main" {
  cidr_block       = "10.0.0.0/16"
}

resource "aws_subnet" "mySubnet" {
  vpc_id            = "${aws_vpc.main.id}"
  availability_zone = "eu-central-1a"
  cidr_block        = "${cidrsubnet(aws_vpc.main.cidr_block, 4, 1)}"
}

resource "aws_instance" "myInstance" {
  # CentOS 7 (x86_64) in Frankfurt, https://wiki.centos.org/Cloud/AWS
  ami = "ami-7cbc6e13"
  instance_type = "t2.large"
  subnet_id = "${aws_subnet.mySubnet.id}"
}

使用terraform版本0.9.5