Fixes #1197 Protecting concurrent access to cdre

CONTRIBUTORS.md

@@ -68,6 +68,7 @@ information, please see the [`CONTRIBUTING.md`](CONTRIBUTING.md) file.
 | @petekelly | Peter Kelly |
 | @vtzan | Vasilios Tzanoudakis |
 | @ccppprogrammer | Sergei Lavrov |
+| @chrisgis333 | Krzysztof Grzyb |
 
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 | @username | First Last |

engine/cdre.go

@@ -331,6 +331,8 @@ func (cdre *CDRExporter) processCDR(cdr *CDR) (err error) {
 		return
 	}
 	// Done with writing content, compute stats here
+	cdre.Lock()
+	defer cdre.Unlock()
 	if cdre.firstCdrATime.IsZero() || cdr.AnswerTime.Before(cdre.firstCdrATime) {
 		cdre.firstCdrATime = cdr.AnswerTime
 	}