Spefify Go version by go.mod

[hmiyado]

resolve: #99

This PR enables to specify Go version by go.mod.

[wangyoucao577]

It might be better to use goversion var directly, something like goversion: go.mod or goversion: ./project1/go.mod. If the INPUT_GOVERSION ends with go.mod, parse it and use its version.
By the way, it also needs a test(in https://github.com/wangyoucao577/go-release-action/blob/master/.github/workflows/autotest.yml) to verify new functions.
Thanks!

[hmiyado]

Thank you for your review.

Fixed goversion to specify the path to go.mod directly.

We are currently working on the test as well.
The existing job generates go.mod with the pre_command option.
If go.mod is specified in goversion, go.mod must exist prior to the timing of pre_command.
We believe a separate job is needed.

[wangyoucao577]

Thank you for your review.

Fixed goversion to specify the path to go.mod directly.

We are currently working on the test as well. The existing job generates go.mod with the pre_command option. If go.mod is specified in goversion, go.mod must exist prior to the timing of pre_command. We believe a separate job is needed.

Oh, it's ok to create another test app for this test.

[hmiyado]

I added new test step in 171948d.
Please check this when you have time.