net: add Source field to OpError (https://go-review.googlesource.com/9231)
net: fix inconsistent errors (https://golang.org/cl/9236)
net: add SocketConn, SocketPacketConn (https://golang.org/cl/9275)
+net: use Go's DNS resolver when system configuration permits (https://golang.org/cl/8945)
net/http: support for setting trailers from a server Handler (https://golang.org/cl/2157)
net/http: ignore the Unix epoch time in ServeContent (https://golang.org/cl/7915)
net/http/cgi: fix REMOTE_ADDR, REMOTE_HOST, add REMOTE_PORT (https://golang.org/cl/4933)
+net/mail: adds AddressParser type (https://golang.org/cl/10392)
net/smtp: add TLSConnectionState accessor (https://golang.org/cl/2151)
os: add LookupEnv (https://golang.org/cl/9791)
os/signal: add Ignore and Reset (https://golang.org/cl/3580)