@NonNull
    public static HttpProtocol parse(@NonNull String protocol) {
        if (protocol.equalsIgnoreCase(HTTP_1_0.protocol)) {
            return HTTP_1_0;
        } else if (protocol.equalsIgnoreCase(HTTP_1_1.protocol)) {
            return HTTP_1_1;
        } else if (protocol.equalsIgnoreCase(H2_PRIOR_KNOWLEDGE.protocol)) {
            return H2_PRIOR_KNOWLEDGE;
        } else if (protocol.equalsIgnoreCase(HTTP_2.protocol)) {
            return HTTP_2;
        } else if (protocol.equalsIgnoreCase(SPDY_3.protocol)) {
            return SPDY_3;
        } else if (protocol.equalsIgnoreCase(QUIC.protocol)) {
            return QUIC;
        } else {
            return UNKNOWN;
        }
    }
Returns the protocol identified by {@code protocol}.

@param protocol A string protocol presents in request line and status line.
@return A HttpProtocol enum.
netbare-core/src/main/java/com/github/megatronking/netbare/http/HttpProtocol.java