Add proof of concept WebApp with basic functionality

TODO:
 • Add arguments to app for port and address
 • Add x-forwarded-for header support for use behind proxies
 • Be able to give response in text, json or html

.gitignore

@@ -0,0 +1 @@
+what-is-my-ip

what-is-my-ip.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"net"
+	"net/http"
+)
+
+func main() {
+	http.HandleFunc("/", getIP)
+	fmt.Println("listening on port 3000")
+	http.ListenAndServe(":3000", nil)
+}
+
+func getIP(w http.ResponseWriter, req *http.Request) {
+	ip, _, err := net.SplitHostPort(req.RemoteAddr)
+	if err != nil {
+		handleError(w, err, "Could not get IP address from request")
+		return
+	}
+	io.WriteString(w, ip+"\n")
+	log.Printf("Give response IP %s\n", ip)
+}
+
+func handleError(resp http.ResponseWriter, err error, message string) {
+	resp.WriteHeader(http.StatusBadRequest)
+	io.WriteString(resp, message)
+	log.Printf("Error handling request: %s (%s)", message, err)
+}