add clarifying error msg

Signed-off-by: Tin Lai <[email protected]>

pkg/config/host.go

@@ -277,7 +277,7 @@ func (h *Host) Options() OptionsList {
 					options = append(options, Option{Name: fieldName, Value: entry})
 				}
 			} else {
-				panic(fmt.Sprintf("Undefined Range type for field '%s'", fieldName))
+				panic(fmt.Sprintf("Undefined Range type for field '%s'.\nIt must contains either of the following value: [ joinByComma, perLine ]", fieldName))
 			}
 			break
 		default: