protected final long getNextDelay(ClientRequestContext ctx, Backoff backoff) {
        return getNextDelay(ctx, backoff, -1);
    }
Returns the next delay which retry will be made after. The delay will be:

<p>{@code Math.min(responseTimeoutMillis, Backoff.nextDelayMillis(int))}

@return the number of milliseconds to wait for before attempting a retry. -1 if the
        {@code currentAttemptNo} exceeds the {@code maxAttempts} or the {@code nextDelay} is after
        the moment which timeout happens.
core/src/main/java/com/linecorp/armeria/client/retry/AbstractRetryingClient.java