go.blog/context: userip support for IPv6 host/port.

Makes example usable on IPv6 systems eg where localhost is ::1.

Fixes golang/go#8486.

LGTM=adg
R=golang-codereviews, dave, adg
CC=golang-codereviews, sameer
https://golang.org/cl/117530044

1 files changed, 6 insertions, 3 deletions

diff --git a/content/context/userip/userip.go b/content/context/userip/userip.go
index ba3851e..616dd04 100644
--- a/content/context/userip/userip.go
+++ b/content/context/userip/userip.go
@@ -6,15 +6,18 @@ import (
 	"fmt"
 	"net"
 	"net/http"
-	"strings"
 
 	"code.google.com/p/go.net/context"
 )
 
 // FromRequest extracts the user IP address from req, if present.
 func FromRequest(req *http.Request) (net.IP, error) {
-	s := strings.SplitN(req.RemoteAddr, ":", 2)
-	userIP := net.ParseIP(s[0])
+	ip, _, err := net.SplitHostPort(req.RemoteAddr)
+	if err != nil {
+		return nil, fmt.Errorf("userip: %q is not IP:port", req.RemoteAddr)
+	}
+
+	userIP := net.ParseIP(ip)
 	if userIP == nil {
 		return nil, fmt.Errorf("userip: %q is not IP:port", req.RemoteAddr)
 	}