Run Go 1.25 online

What's in Go 1.25

• testing/synctest out of experimental — deterministic tests for concurrent code.
• Go 1.25 detects Linux cgroup CPU limits and sizes GOMAXPROCS accordingly.
• go doc -http launches a local godoc server on demand.

What you get in Go 1.25

Clicking "Run now" opens the playground with this exact code and a matching test case — passes on first Run.

package main
import "fmt"
func main(){var n int;fmt.Scan(&n);fmt.Println(n*2)}

How ls-judge runs Go 1.25

Every submission is compiled and executed inside its own Firecracker microVM — the same isolation primitive AWS Lambda uses. No shared container, no shared kernel with other users' code. The Go 1.25toolchain shipped with the microVM is the real thing (not a browser-side emulation): syscalls behave the way they do in production, and the compile / runtime behaviour matches what you would see on your own machine with that version installed.

Feed stdin from the Tests panel, watch verdicts stream per test case over a WebSocket. Free to use, no sign-up, works from any browser.