code: func FnGetAZs(name string, input interface{}, template interface{}) interface{} {
  
  	// Check the input is a string
  	if region, ok := input.(string); ok {
  		if region == "" {
  			region = "us-east-1"
  		}
  
  		if azs, ok := AZs[region]; ok {
  			return azs
  		} else {
  			//assume 3 AZs per region
  			return buildAZs(region, "a", "b", "c")
  		}
  	}
  
  	return nil
  }
docs: // FnGetAZs resolves the 'Fn::GetAZs' AWS CloudFormation intrinsic function.
  // See: http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-getavailabilityzones.html