(untested) move unsafe string conversion to pkg

* fix invalid UDP f/e start when no workers provided
* add bench for entire server

pkg/str2bytes/str2bytes.go

@@ -0,0 +1,21 @@
+// Package str2bytes provides fast, but unsafe functions to convert string to []byte
+// or vice versa.
+package str2bytes
+
+import "unsafe"
+
+// StringToBytes converts string to slice of bytes
+// without allocation. Note, that returned slice
+// must NOT be modified, since strings in Go are
+// immutable.
+// See unsafe.Slice.
+func StringToBytes(s string) []byte {
+	return unsafe.Slice(unsafe.StringData(s), len(s))
+}
+
+// BytesToString converts slice of bytes to string
+// without allocation.
+// See unsafe.String
+func BytesToString(b []byte) string {
+	return unsafe.String(unsafe.SliceData(b), len(b))
+}