public ClientFactoryBuilder idleTimeoutMillis(long idleTimeoutMillis) {
        return idleTimeoutMillis(idleTimeoutMillis, Flags.defaultClientKeepAliveOnPing());
    }
Sets the idle timeout of a socket connection in milliseconds. The connection is closed if there is no
request in progress for the given amount of time.
core/src/main/java/com/linecorp/armeria/client/ClientFactoryBuilder.java