Remote IP Address with Go (X-Real-Ip and X-Forwarded-For included)

remoteip.go

package lib

import (
	"net"
	"net/http"
	"strings"
)

func GetIPAddr(r *http.Request) string {
	ipaddr, _, _ := net.SplitHostPort(r.RemoteAddr)
	PrivateRanges := []string{"10.0.0.0/8", "172.16.0.0/12", "192.168.0.0/16"}
	for i, _ := range PrivateRanges {
		if _, subnet, _ := net.ParseCIDR(PrivateRanges[i]); subnet.Contains(net.ParseIP(ipaddr)) {
			for _, h := range []string{"X-Forwarded-For", "X-Real-Ip"} {
				for _, ip := range strings.Split(r.Header.Get(h), ",") {
					RealIp := net.ParseIP(strings.Replace(ip, " ", "", -1))
					if check := net.ParseIP(RealIp.String()); check != nil {
						ipaddr = RealIp.String()
					}
				}
			}
		}
	}
	return ipaddr
}