update to tf 0.13

[mcalhoun]

what

• update module to support terraform 0.13
• move from dep to gomod
• update to current style context.tf

why

• update outdated dependencies and constraints

[aknysh]

Suggested change

	aws = "~> 2.0"
	aws = ">= 2.0"

use >= for all other providers as well

[mcalhoun]

Thanks for the suggestion. Wouldn't this be risky if a breaking change comes along in provider v3 or v4 that makes our module stop working?

[aknysh]

there is a risk, but the modules usually work ok with v3.
Otherwise, we'd have to modify all our hundreds of modules again and again for the next versions, which is way more work than to fix a module or a few if they are broken by the new provider version

[aknysh]

people should pin to a release, so even if the new release breaks something, the previous releases should work

[mcalhoun]

Not necessarily, I actually think that's the danger.

If the consumer is pinning to v1 of the module and the module allows a provider >= 2.0 and a new provider (say v3) is released, the consumer could get v3 of the provider, which could have backward-incompatible changes. The AWS v2 to AWS v3 is a perfect example as there are a bunch of breaking changes.

I'm fine following the convention here but just wanted to make sure I pointed out the risk and discussed the thought process.

[aknysh]

yes, we allow all versions, and we know about the risks.
It's still better than to update and test hundreds of modules for each new version of the providers

[aknysh]

@mcalhoun LGTM, a few comments:

1. Update examples/complete to context.tf similar to https://github.com/cloudposse/terraform-aws-datadog-integration/tree/master/examples/complete

2. run these commands from the root of the repo

make init
make github/init
make readme

3. Use the new provider syntax (the old one is deprecated and will throw errors in the next TF release
   https://github.com/cloudposse/terraform-aws-datadog-integration/blob/master/versions.tf#L4

[mcalhoun]

Thanks for the review @aknysh I'll make those changes now!

[mcalhoun]

/test all

[mcalhoun]

/test all

[mcalhoun]

/test all

[aknysh]

in examples/complete/main.tf, this

module "sns" {
  source    = "../../"
  namespace = var.namespace
  name      = var.name
  stage     = var.stage
}

should be updated to this 

module "sns" {
source = "../../"

context = module.this.context
}

see https://github.com/cloudposse/terraform-aws-datadog-integration/blob/master/examples/complete/main.tf

[mcalhoun]

/test all

[mcalhoun]

in examples/complete/main.tf, this

module "sns" {
source = "../../"
namespace = var.namespace
name = var.name
stage = var.stage
}

should be updated to this

module "sns" {
source = "../../"

context = module.this.context
}

be2cdc4

[aknysh]

Suggested change

	source = "git::https://github.com/cloudposse/terraform-null-label.git?ref=tags/0.19.2"
	source = "git::https://github.com/cloudposse/terraform-null-label.git?ref=tags/0.20.0"

[mcalhoun]

/test all