add workerpool to util

src/util/workerpool.go

@@ -0,0 +1,29 @@
+package util
+
+import "runtime"
+
+var workerPool chan func()
+
+func init() {
+	maxProcs := runtime.GOMAXPROCS(0)
+	if maxProcs < 1 {
+		maxProcs = 1
+	}
+	workerPool = make(chan func(), maxProcs)
+	for idx := 0; idx < maxProcs; idx++ {
+		go func() {
+			for f := range workerPool {
+				f()
+			}
+		}()
+	}
+}
+
+// WorkerGo submits a job to a pool of GOMAXPROCS worker goroutines.
+// This is meant for short non-blocking functions f() where you could just go f(),
+// but you want some kind of backpressure to prevent spawning endless goroutines.
+// WorkerGo returns as soon as the function is queued to run, not when it finishes.
+// In Yggdrasil, these workers are used for certain cryptographic operations.
+func WorkerGo(f func()) {
+	workerPool <- f
+}