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Go Templates

Full support for Go templates through a series of predefined named fields allows `dns53`` to support a dynamic configuration where needed.

Table Key

This is a living table and will change as new features are released.

  • : the metadata was formatted to ensure it is URL compliant
  • : the metadata was retrieved from EC2 instance tags; this feature must be enabled

Named Fields

The following named fields directly access metadata about your EC2 from the Instance Metadata Service (IMDS).

Named Field Description Example
{{.IPv4}} the private IPv4 address of the EC2 instance 10-0-1-182
{{.Region}} the region of the EC2 instance eu-west-2
{{.VPC}} the VPC ID of where the EC2 instance was launched vpc-016d173db537793d1
{{.AZ}} the availability zone (AZ) of the EC2 instance eu-west-2a
{{.InstanceID}} the unique ID of the EC2 instance i-03e092f544905abb2
{{.Name}} a name assigned to the EC2 instance dev-ec2

Dynamic Tags

As the IMDS service exposes all EC2 instance tags (once enabled), you can access them in much the same way as other named fields. Internally dns53 stores all tags within a Tags map and provides access to them in two ways.

  1. Directly through property chaining1, {{.Tags.Key}}
  2. Or by using the inbuilt Go templating index function, {{index .Tags "Key"}}
Named Field Description Examples
{{.Tags.Ec2Role}} the role assigned to this EC2 instance development
{{index .Tags "ec2:role"}} the role assigned to this EC2 instance development

  1. Amazon's tag naming and usage guidelines permit characters not supported by Go templating for property chaining, namely [+ - = . , _ : @]. A best efforts approach was adopted to clean the name of the tag; for further details, please read the following documentation. ↩