util: add GoWait function

GoWait will increase the provided waitGroup on start and execute a goroutine
that will run the provided functions and then decrease the waitGroup

internal/util/goroutine.go

@@ -0,0 +1,25 @@
+// Copyright 2019 Sorint.lab
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package util
+
+import "sync"
+
+func GoWait(wg *sync.WaitGroup, f func()) {
+	wg.Add(1)
+	go func() {
+		f()
+		wg.Done()
+	}()
+}