added mdns package to networking category

README.md

@@ -447,6 +447,7 @@ Join us on IRC at **#awesome-go** on freenode [web access](http://webchat.freeno
 * [gotcp](https://github.com/gansidui/gotcp) - A Go package for quickly writing tcp applications
 * [graval](https://github.com/koofr/graval) - An experimental FTP server framework.
 * [linkio](https://github.com/ian-kent/linkio) - Network link speed simulation for Reader/Writer interfaces
+* [mdns](https://github.com/hashicorp/mdns) - Simple mDNS (Multicast DNS) client/server library in Golang
 * [portproxy](https://github.com/aybabtme/portproxy) - Simple TCP proxy which adds CORS support to API's which don't support it.
 * [sftp](https://github.com/pkg/sftp) - Package sftp implements the SSH File Transfer Protocol as described in https://filezilla-project.org/specs/draft-ietf-secsh-filexfer-02.txt.
 * [tcp_server](https://github.com/firstrow/tcp_server) - A Go library for building tcp servers faster