long getGracePeriod() {
            return this.gracePeriod;
        }
Closes this channel factory and the channels created by this instance. The shutdown happens in two phases, first
an orderly shutdown is initiated on all channels and then the method waits for all channels to terminate. If the
channels don't have terminated after 60 seconds then they will be forcefully shutdown.
grpc-client-spring-boot-starter/src/main/java/net/devh/boot/grpc/client/channelfactory/AbstractChannelFactory.java