What is runtime/debug in Go?

Question

Accepted Answer

runtime/debug is a package for **debugging and managing** the Go runtime.

```go
import "runtime/debug"

func main() {
    // Build information
    info, ok := debug.ReadBuildInfo()
    if ok {
        fmt.Println("Go version:", info.GoVersion)
        fmt.Println("Module:", info.Main.Path)
        for _, dep := range info.Deps {
            fmt.Printf("  %s@%s
", dep.Path, dep.Version)
        }
    }

// Stack of all goroutines
    buf := make([]byte, 1<<20)
    n := runtime.Stack(buf, true)  // true = all goroutines
    fmt.Println(string(buf[:n]))

// GC configuration
    debug.SetGCPercent(200)  // GC when memory doubles
    debug.SetMemoryLimit(1 << 30)  // 1GB limit (Go 1.19+)

// Limiting goroutine count
    debug.SetMaxThreads(500)

// Limiting stack
    debug.SetMaxStack(256 << 20)  // 256MB

// Disable GC
    debug.SetGCPercent(-1)
    debug.SetMemoryLimit(0)
    runtime.GC()  // Collect garbage before disabling
}

// Stack trace for a specific goroutine
func getStackTrace() string {
    buf := make([]byte, 1<<16)
    n := runtime.Stack(buf, false)  // false = current only
    return string(buf[:n])
}

// Freeze GC (for debugging)
runtime.GC()
debug.FreeOSMemory()  // Free OS memory
```

**Useful functions:**
- ReadBuildInfo — build information.
- SetGCPercent/SetMemoryLimit — GC configuration.
- SetMaxThreads — OS thread limit.

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