add memory limit

runner/limiter.go

@@ -0,0 +1,15 @@
+package runner
+
+import "os/exec"
+
+type limiter interface {
+	prepare(cmd *exec.Cmd) error
+	afterStart(cmd *exec.Cmd) error
+	collect() limitStats
+	cleanup()
+}
+
+type limitStats struct {
+	PeakMemory     int64
+	MemoryExceeded bool
+}