code: func readAWSCloudConfig(config io.Reader, metadata EC2Metadata) (*CloudConfig, error) {
  	var cfg CloudConfig
  	var err error
  
  	if config != nil {
  		err = gcfg.ReadInto(&cfg, config)
  		if err != nil {
  			return nil, err
  		}
  	}
  
  	if cfg.Global.Zone == "" {
  		if metadata != nil {
  			glog.Info("Zone not specified in configuration file; querying AWS metadata service")
  			cfg.Global.Zone, err = getAvailabilityZone(metadata)
  			if err != nil {
  				return nil, err
  			}
  		}
  		if cfg.Global.Zone == "" {
  			return nil, fmt.Errorf("no zone specified in configuration file")
  		}
  	}
  
  	return &cfg, nil
  }
docs: // readAWSCloudConfig reads an instance of AWSCloudConfig from config reader.