public ServerBuilder connectionDrainDurationMicros(long durationMicros) {
        checkArgument(connectionDrainDurationMicros >= 0,
                      "connectionDrainDurationMicros: %s (expected: >= 0)",
                      connectionDrainDurationMicros);
        connectionDrainDurationMicros = durationMicros;
        return this;
    }
Sets the connection drain duration in micros for the connection shutdown.
At the beginning of the connection drain server signals the clients that the connection shutdown is
imminent but still accepts in flight requests.
After the connection drain end server stops accepting new requests.
Also, see {@link ServerBuilder#connectionDrainDuration(Duration)}.

<p>
Note that HTTP/1 doesn't support draining as described here, so for HTTP/1 drain duration
is always {@code 0}, which means the connection will be closed immediately as soon as
the current in-progress request is handled.
</p>

@param durationMicros the drain duration. {@code 0} disables the drain.
core/src/main/java/com/linecorp/armeria/server/ServerBuilder.java