feat(middleware): add X-Forwarded-For middleware

close #73

pkg/api/routes.go

@@ -9,6 +9,7 @@ import (
 )
 
 var commonMiddlewares = middleware.Middlewares{
+	middleware.XFF,
 	middleware.Cors,
 	middleware.Logger,
 	middleware.Tracing(nextRequestID),

pkg/middleware/xff.go

@@ -0,0 +1,27 @@
+package middleware
+
+import (
+	"net"
+	"net/http"
+)
+
+const xForwardedFor = "X-Forwarded-For"
+
+func getIP(req *http.Request) string {
+	ip, _, err := net.SplitHostPort(req.RemoteAddr)
+	if err != nil {
+		return req.RemoteAddr
+	}
+	return ip
+}
+
+// XFF is a middleware to identifying the originating IP address using X-Forwarded-For header
+func XFF(inner http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		xff := r.Header.Get(xForwardedFor)
+		if xff == "" {
+			r.Header.Set(xForwardedFor, getIP(r))
+		}
+		inner.ServeHTTP(w, r)
+	})
+}