GRPCClient getClient() {
        if (Objects.isNull(client)) {
            synchronized (GRPCRemoteClient.class) {
                if (Objects.isNull(client)) {
                    this.client = new GRPCClient(address.getHost(), address.getPort(), sslContext);
                }
            }
        }
        return client;
    }
Get channel state by the true value of request connection.

@return a channel when the state to be ready
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/remote/client/GRPCRemoteClient.java