public GraphqlServiceBuilder executionIdGenerator(ExecutionIdGenerator executionIdGenerator) {
        checkState(graphql == null, "graphql() and executionIdGenerator() are mutually exclusive.");
        this.executionIdGenerator = requireNonNull(executionIdGenerator, "executionIdGenerator");
        return this;
    }
Sets the {@link ExecutionIdGenerator}.
If not specified, {@link ExecutionIdGenerator#of()} is used by default.
graphql/src/main/java/com/linecorp/armeria/server/graphql/GraphqlServiceBuilder.java