在Go中编组动态JSON字段标签

Question

I'm trying to generate JSON for a Terraform file. Because I (think I) want to use marshalling instead of rolling my own JSON, I'm using Terraforms JSON format instead of the 'native' TF format.

{
  "resource": [
    {
      "aws_instance": {
        "web1": {
          "some": "data"
        }
    }]
}

resource and aws_instance are static identifiers while web1 in this case is the random name. Also it wouldn't be unthinkable to also have web2 and web3.

type Resource struct {
    AwsResource AwsResource `json:"aws_instance,omitempty"`
}

type AwsResource struct {
    AwsWebInstance AwsWebInstance `json:"web1,omitempty"`
}

The problem however; how do do I generate random/variable JSON keys with Go's field tags?

I have a feeling the answer is "You don't". What other alternatives do I have then?

Answer 1

In most cases where there are names not known at compile time, a map can be used:

type Resource struct {
    AWSInstance map[string]AWSInstance `json:"aws_instance"`
}

type AWSInstance struct {
    AMI string `json:"ami"`
    Count int `json:"count"`
    SourceDestCheck bool `json:"source_dest_check"`
    // ... and so on
}

Here's an example showing how to construct the value for marshalling:

r := Resource{
    AWSInstance: map[string]AWSInstance{
        "web1": AWSInstance{
            AMI:   "qdx",
            Count: 2,
        },
    },
}

playground example