Preventing and Detecting Goroutine Leaks

In Go, starting a goroutine is as simple as the go keyword. But an abandoned goroutine that never exits is a permanent memory leak — its stack and heap allocations cannot be reclaimed by the garbage collector.

The Classic Nil Channel / Blocked Receive Leak

func QueryFirst(ctx context.Context, urls []string) string {
    ch := make(chan string) // Unbuffered!
    for _, url := range urls {
        go func(u string) {
            ch <- fetch(u) // Blocked forever if context cancels or first response wins!
        }(url)
    }
    return <-ch
}

Detection Tools

go.uber.org/goleak: Catch leaked goroutines in unit tests before merging to main:
```
func TestMain(m *testing.M) {
    goleak.VerifyTestMain(m)
}
```
Runtime metrics: Track runtime.NumGoroutine() in production dashboards to spot upward-trending slopes.

See also the full guide on managing lifecycles in the blog: Managing Goroutine Lifecycles in Go.