Go definitely popularized concurrency for the modern era, but coroutines themselves are ancient tech. Melvin Conway coined the term in 1963 and Simula had them by '67.

It’s also worth noting that the specific 'coroutine' model most languages are adding today (JS, Rust, Python) is based on C#'s async/await.

Go actually rejected that approach in favor of Green Threads (Goroutines, not coroutines), so technically it popularized the alternative to what everyone else is doing.