public static InitiateConnectionShutdown of(long drainDurationMicros) {
        // Clamp drain duration to 0. Negative values are used internally to fallback to the currently
        // configured drain duration.
        if (drainDurationMicros <= 0) {
            return NO_DRAIN;
        }
        return new InitiateConnectionShutdown(drainDurationMicros);
    }
Returns {@link InitiateConnectionShutdown} event with custom drain duration in microseconds.
Negative values are a valid input - negative duration may be passed as a result of the time arithmetics,
in that case drain duration will be set to 0.
core/src/main/java/com/linecorp/armeria/internal/common/InitiateConnectionShutdown.java