Code cleanup (#1640)

- Replaced time.Now().Sub() with time.Since()
- Replaced unnecessary string/byte slice conversions
- Removed obsolete return and value assignment in range loop

src/terminal.go

@@ -1532,7 +1532,7 @@ func (t *Terminal) Loop() {
 					cmd.Wait()
 					finishChan <- true
 					if out.Len() > 0 || !<-updateChan {
-						t.reqBox.Set(reqPreviewDisplay, string(out.Bytes()))
+						t.reqBox.Set(reqPreviewDisplay, out.String())
 					}
 				} else {
 					t.reqBox.Set(reqPreviewDisplay, "")