When we talk about Go's concurrency, it's impossible not to talk about history. In the last decades, we saw an improvement in the speed of CPUs until we reached the hardware limits imposed by current hardware materials, design, and architectures. When we reached this point, we started to play with the first multicore computers, the first double CPU motherboards, and then single CPUs with more than one core in their heart.
Unfortunately, the languages we are using are still the ones created when we had single core CPUs, such as Java or C++. While being terrific systems languages, they lack a proper concurrency support by design. You can develop concurrent apps in both of the languages used in your project by using third party tools or by developing your own (not a very easy task).
Go's concurrency was designed with these caveats in mind. The creators wanted garbage collected and procedural language that is familiar for newcomers, but which, at the same time...