code: func InjectMessages(m Messages) {
  	for k, v := range m {
  		if _, ok := msgs[k]; ok {
  			panic(fmt.Sprintf("duplicated error: %d", k))
  		}
  		msgs[k] = v
  	}
  }
docs: // InjectMessages injects errors messages into a global message map. Any
  // package with own errors defined should call this function during its
  // initialisation (i.e. in init() function).