public static long defaultMaxServerConnectionAgeMillis() {
        return DEFAULT_MAX_SERVER_CONNECTION_AGE_MILLIS;
    }
Returns the default server-side max age of a connection for keep-alive in milliseconds.
If the value of this flag is greater than {@code 0}, a connection is disconnected after the specified
amount of the time since the connection was established.

<p>The default value of this flag is
{@value DefaultFlagsProvider#DEFAULT_MAX_SERVER_CONNECTION_AGE_MILLIS}.
Specify the {@code -Dcom.linecorp.armeria.defaultMaxServerConnectionAgeMillis=<integer>} JVM option
to override the default value. If the specified value was smaller than 1 second,
bumps the max connection age to 1 second.

@see ServerBuilder#maxConnectionAgeMillis(long)
core/src/main/java/com/linecorp/armeria/common/Flags.java