This mini-book provides a brief overview of many concurrency topics in Go. Each topic comes with interactive examples — feel free to experiment with them by changing the code and clicking Run . There's also a PDF version with static examples. This is a quick refresher on Go concurrency, not a beginner's guide. If you want to learn concurrency from the ground up with practical exercises, check out my other book — Gist of Go: Concurrency . The book is AI-free. Goroutines  • Channels  • Select  • Pipelines  • Time  • Context  • Wait groups  • Data races  • Race conditions  • Mutexes  • Semaphores  • Signaling  • Run once  • Object pool  • Atomics  • Testing  • Scheduling  • Diagnostics  • Final thoughts # Goroutines The foundation of concurrency in Go is goroutines – functions started with the go keyword: func main () { var wg sync . WaitGroup wg . Add ( 2 ) go func () { defer wg . Done () fmt .…