In this paper we deal with the impact of multi and many-core processor architectures on simulation. Despite the fact that modern CPUs have an increasingly large number of cores, most softwares are still unable to take advantage of them. In the last years, many tools, programming languages and general methodologies have been proposed to help building scalable applications for multi-core architectures, but those solutions are somewhat limited. Parallel and distributed simulation is an interesting application area in which efficient and scalable multi-core implementations would be desirable. In this paper we investigate the use of the Go Programming Language to implement optimistic parallel simulations based on the Time Warp mechanism. Specifically, we describe the design, implementation and evaluation of a new parallel simulator. The scalability of the simulator is studied when in presence of a modern multi-core CPU and the effects of the Hyper-Threading technology on optimistic simulation are analyzed.