private static String errorStr(long errorCode) {
        final Http2Error error = Http2Error.valueOf(errorCode);
        return error != null ? error.toString() + '(' + errorCode + ')'
                             : "UNKNOWN(" + errorCode + ')';
    }
Returns {@code true} if the connection has received a GOAWAY frame with non-zero error code.
core/src/main/java/com/linecorp/armeria/internal/common/Http2GoAwayHandler.java