Pass vault server options to plugin SDK

This is about vault plugin development SDK. When launching a vault server, I could set up the log-level option. How could I catch this value in SDK?

Specifically, I am using

plugin.ServeMultiplex(&plugin.ServeOpts{
BackendFactoryFunc: func(ctx context.Context, c *logical.BackendConfig) (logical.Backend, error) {
c.Logger.SetLevel(LOG_LEVEL_FROM_VAULT_SERVER_NEEDED)
return myFactory(ctx, c, …)
},
TLSProviderFunc: tlsProviderFunc,
})

to start the server, and want to have a consistent log level in both the server and the plugin.

Thanks.