sessionConcurrency

@Configuration
@EnableWebFluxSecurity
open class SecurityConfig {

 @Bean
 open fun springWebFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain {
     return http {
         sessionManagement {
             sessionConcurrency {
                 maximumSessions = { authentication -> Mono.just(1) }
             }
         }
      }
  }
}