If you have worked in other languages, such as Java or C/C++, you are probably familiar with the notion of concurrency. It is the ability of a program to run two or more paths of execution independently. This is usually done by exposing a thread primitive directly to the programmer to create and manage concurrency.
Go has its own concurrency primitive called the goroutine, which allows a program to launch a function (routine) to execute independently from its calling function. Goroutines are lightweight execution contexts that are multiplexed among a small number of OS-backed threads and scheduled by Go's runtime scheduler. That makes them cheap to create without the overhead requirements of true kernel threads. As such, a Go program can initiate thousands (even hundreds of thousands) of goroutines with minimal impact on performance and resource degradation.