Update go.mod to 1.19

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 70.37%. Comparing base (17e9f5f) to head (745ade0).

:exclamation: Current head 745ade0 differs from pull request most recent head 6e3e847. Consider uploading reports for the commit 6e3e847 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #54 +/- ## ======================================= Coverage 70.37% 70.37% ======================================= Files 8 8 Lines 1664 1664 ======================================= Hits 1171 1171 Misses 467 467 Partials 26 26 ``` | [Flag](https://app.codecov.io/gh/pion/opus/pull/54/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pion) | Coverage Δ | | |---|---|---| | [go](https://app.codecov.io/gh/pion/opus/pull/54/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pion) | `70.37% <ø> (ø)` | | | [wasm](https://app.codecov.io/gh/pion/opus/pull/54/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pion) | `69.05% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pion#carryforward-flags-in-the-pull-request-comment) to find out more.

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[edaniels]

Looks fine