code: func (r *Route) Schemes(schemes ...string) *Route {
  	for k, v := range schemes {
  		schemes[k] = strings.ToLower(v)
  	}
  	if len(schemes) > 0 {
  		r.buildScheme = schemes[0]
  	}
  	return r.addMatcher(schemeMatcher(schemes))
  }
docs: // Schemes adds a matcher for URL schemes.
  // It accepts a sequence of schemes to be matched, e.g.: "http", "https".