code: func (c *ConfigLookup) Lookup(repoInfo *registry.RepositoryInfo) types.AuthConfig {
  	if c.ConfigFile == nil || repoInfo == nil || repoInfo.Index == nil {
  		return types.AuthConfig{}
  	}
  	return registry.ResolveAuthConfig(c.ConfigFile.AuthConfigs, repoInfo.Index)
  }
docs: // Lookup uses a Docker config file to lookup authentication information