code: func portFromHostContainer(hostContainer string) (p Port, err error) {
  	var host, container int
  	parts := strings.SplitN(hostContainer, ":", 2)
  	host, err = toPort(parts[0])
  	if err != nil {
  		return
  	}
  	container, err = toPort(parts[1])
  	if err != nil {
  		return
  	}
  
  	p.Host = host
  	p.Container = container
  	return
  }
docs: // Parses a `hostport:containerport` string into a Port.