code: func (c *LoggerCollection) SetHandler(re *regexp.Regexp, handler Handler) {
  	c.mtx.Lock()
  	defer c.mtx.Unlock()
  
  	if re == nil {
  		c.handler = handler
  	}
  	for name, logger := range c.loggers {
  		if re == nil || re.MatchString(name) {
  			logger.setHandler(handler)
  		}
  	}
  }
docs: // SetHandler will set the current log handler for all loggers with names that
  // match a provided regular expression. If the regular expression is nil, then
  // all loggers match.