Fixed Error return value of is not checked (errcheck)

collectors/diskstatMetric.go

@@ -72,10 +72,18 @@ func (m *DiskstatCollector) Read(interval time.Duration, output chan lp.CCMessag
 
 	file, err := os.Open(MOUNTFILE)
 	if err != nil {
-		cclog.ComponentError(m.name, err.Error())
+		cclog.ComponentError(
+			m.name,
+			fmt.Sprintf("Read(): Failed to open file '%s': %v", MOUNTFILE, err))
 		return
 	}
-	defer file.Close()
+	defer func() {
+		if err := file.Close(); err != nil {
+			cclog.ComponentError(
+				m.name,
+				fmt.Sprintf("Read(): Failed to close file '%s': %v", MOUNTFILE, err))
+		}
+	}()
 
 	part_max_used := uint64(0)
 	scanner := bufio.NewScanner(file)