code: func getH2Settings(h http.Header) ([]http2.Setting, error) {
  	vals, ok := h[textproto.CanonicalMIMEHeaderKey("HTTP2-Settings")]
  	if !ok {
  		return nil, errors.New("missing HTTP2-Settings header")
  	}
  	if len(vals) != 1 {
  		return nil, fmt.Errorf("expected 1 HTTP2-Settings. Got: %v", vals)
  	}
  	settings, err := decodeSettings(vals[0])
  	if err != nil {
  		return nil, fmt.Errorf("invalid HTTP2-Settings: %q", vals[0])
  	}
  	return settings, nil
  }
docs: // getH2Settings returns the []http2.Setting that are encoded in the
  // HTTP2-Settings header.