public CompletableFuture<Void> start() {
        return startStop.start(true);
    }
Starts this {@link Server} to listen to the {@link ServerPort}s specified in the {@link ServerConfig}.
Note that the startup procedure is asynchronous and thus this method returns immediately. To wait until
this {@link Server} is fully started up, wait for the returned {@link CompletableFuture}:
<pre>{@code
ServerBuilder builder = Server.builder();
...
Server server = builder.build();
server.start().get();
}</pre>
core/src/main/java/com/linecorp/armeria/server/Server.java