code: func (rc *regexpCache) Get(pattern string) (re *regexp.Regexp, err error) {
  	var ok bool
  
  	if re, ok = rc.get(pattern); !ok {
  		re, err = regexp.Compile(pattern)
  		if err != nil {
  			return nil, err
  		}
  		rc.set(pattern, re)
  	}
  
  	return re, nil
  }
docs: // Get retrieves a regexp object from the cache based upon the pattern.
  // If the pattern is not found in the cache, create one