added to docs

filtered_router.go

@@ -7,6 +7,37 @@ package flog
 // re-Route a 'message' (and 'context') to, but only on the
 // condition that 'filterFn' returns 'true' for the 'message'
 // and 'context' passed to it.
+//
+// An example for 'filterFn' is the following.
+//
+//	func filterError(message string, context map[string]interface{})bool) bool {
+//		if datum, ok := context["error"]; !ok {
+//			return false
+//		} else if _, ok := datum.(error); !ok {
+//			return false
+//		} else {
+//			return true
+//		}
+//	}
+//
+// This func will make it so only re-route messages whose context #1 has the key "error"
+// and #2 the value of the context at key "key" fits the builtin Go 'error' interface.
+//
+// Also, a rather useless example, but a 'filterFn' that would reject all messages (and
+// contexts) is:
+//
+//	func filterRejectAll(message string, context map[string]interface{})bool) bool {
+//		return false
+//	}
+//
+//
+// And also, another rather useless example, but a 'filterFn' that would allow all messages
+// (and contexts) is:
+//
+//	func filterAcceptAll(message string, context map[string]interface{})bool) bool {
+//		return true
+//	}
+//
 func NewFilteredRouter(subrouter Router, filterFn func(string, map[string]interface{})bool) *FilteredRouter {
 	router := FilteredRouter{
 		subrouter:subrouter,