}
	}
	if err := http2checkValidHTTP2RequestHeaders(opts.Header); err != nil {
		return err
	}

	// The RFC effectively limits promised requests to GET and HEAD:
	// "Promised requests MUST be cacheable [GET, HEAD, or POST], and MUST be safe [GET or HEAD]"
	// http://tools.ietf.org/html/rfc7540#section-8.2
	if opts.Method != "GET" && opts.Method != "HEAD" {
		return fmt.Errorf("method %q must be GET or HEAD", opts.Method)