chore: using error log instead of errorf

[ShiningRush]

resolve #38 error format

[codecov[bot]]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (2c1880b) 60.02% compared to head (2c94594) 60.02%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #39 +/- ## ======================================= Coverage 60.02% 60.02% ======================================= Files 28 28 Lines 2972 2972 ======================================= Hits 1784 1784 Misses 1045 1045 Partials 143 143 ``` | [Files](https://app.codecov.io/gh/ShiningRush/fastflow/pull/39?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Vinci+Xu) | Coverage Δ | | |---|---|---| | [pkg/mod/parser.go](https://app.codecov.io/gh/ShiningRush/fastflow/pull/39?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Vinci+Xu#diff-cGtnL21vZC9wYXJzZXIuZ28=) | `86.05% <0.00%> (ø)` | |

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