feat: Waku v2 bridge

Issue #12610

vendor/github.com/rs/dnscache/README.md

@@ -0,0 +1,78 @@
+# DNS Lookup Cache
+
+[![license](http://img.shields.io/badge/license-MIT-red.svg?style=flat)](https://raw.githubusercontent.com/rs/dnscache/master/LICENSE)
+[![Go Report Card](https://goreportcard.com/badge/github.com/rs/dnscache)](https://goreportcard.com/report/github.com/rs/dnscache)
+[![Build Status](https://travis-ci.org/rs/dnscache.svg?branch=master)](https://travis-ci.org/rs/dnscache)
+[![Coverage](http://gocover.io/_badge/github.com/rs/dnscache)](http://gocover.io/github.com/rs/dnscache)
+[![godoc](http://img.shields.io/badge/godoc-reference-blue.svg?style=flat)](https://godoc.org/github.com/rs/dnscache)
+
+The dnscache package provides a DNS cache layer to Go's `net.Resolver`.
+
+# Install
+
+Install using the "go get" command:
+
+```
+go get -u github.com/rs/dnscache
+```
+
+# Usage
+
+Create a new instance and use it in place of `net.Resolver`. New names will be cached. Call the `Refresh` method at regular interval to update cached entries and cleanup unused ones.
+
+```go
+resolver := &dnscache.Resolver{}
+
+// First call will cache the result
+addrs, err := resolver.LookupHost(context.Background(), "example.com")
+
+// Subsequent calls will use the cached result
+addrs, err = resolver.LookupHost(context.Background(), "example.com")
+
+// Call to refresh will refresh names in cache. If you pass true, it will also
+// remove cached names not looked up since the last call to Refresh. It is a good idea
+// to call this method on a regular interval.
+go func() {
+    t := time.NewTicker(5 * time.Minute)
+    defer t.Stop()
+    for range t.C {
+        resolver.Refresh(true)
+    }
+}()
+```
+
+If you are using an `http.Transport`, you can use this cache by specifying a `DialContext` function:
+
+```go
+r := &dnscache.Resolver{}
+t := &http.Transport{
+    DialContext: func(ctx context.Context, network string, addr string) (conn net.Conn, err error) {
+        host, port, err := net.SplitHostPort(addr)
+        if err != nil {
+            return nil, err
+        }
+        ips, err := r.LookupHost(ctx, host)
+        if err != nil {
+            return nil, err
+        }
+        for _, ip := range ips {
+            var dialer net.Dialer
+            conn, err = dialer.DialContext(ctx, network, net.JoinHostPort(ip, port))
+            if err == nil {
+                break
+            }
+        }
+        return
+    },
+}
+```
+
+If addition to the `Refresh` method, you can `RefreshWithOptions`. This method adds an option to persist resource records
+on failed lookups
+```go
+r := &Resolver{}
+options := dnscache.ResolverRefreshOptions{}
+options.ClearUnused = true
+options.PersistOnFailure = false
+resolver.RefreshWithOptions(options)
+```