public static NetBare get() {
        return Holder.INSTANCE;
    }
NetBare is a single instance, we can use this class to config and manage the NetBare service.
The NetBare service is an implement class of {@link VpnService}, before starting this service,
should call {@link #prepare()} to check the vpn state.

Start and stop the NetBare service:
<pre>
<code>
    NetBare.get().start(config);
    NetBare.get().stop();
</code>
</pre>

@author Megatron King
@since 2018-10-07 09:28
netbare-core/src/main/java/com/github/megatronking/netbare/NetBare.java