public SELF backoff(Backoff backoff) {
        this.backoff = requireNonNull(backoff, "backoff");
        return self();
    }
Sets the {@link Backoff} that determines how much delay should be inserted between queries when a DNS
server sent an error response. {@code Backoff.exponential(1000, 32000).withJitter(0.2)} is used by
default.
core/src/main/java/com/linecorp/armeria/client/endpoint/dns/DnsEndpointGroupBuilder.java