Add call-id via middleware

Signed-off-by: Alex Ellis <alexellis2@gmail.com>

gateway/handlers/callid_middleware.go

@@ -0,0 +1,24 @@
+package handlers
+
+import (
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/docker/distribution/uuid"
+)
+
+// MakeCallIDMiddleware middleware tags a request with a uid
+func MakeCallIDMiddleware(next http.HandlerFunc) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		start := time.Now()
+		callID := uuid.Generate().String()
+		r.Header.Add("X-Call-Id", callID)
+		w.Header().Add("X-Call-Id", callID)
+
+		r.Header.Add("X-Start-Time", fmt.Sprintf("%d", start.UTC().UnixNano()))
+		w.Header().Add("X-Start-Time", fmt.Sprintf("%d", start.UTC().UnixNano()))
+
+		next(w, r)
+	}
+}