Running mutation tests against Ooze itself fails

After introducing https://github.com/gtramontina/ooze/pull/5, running mutation tests against Ooze itself (and I think it is safe to assume that other projects too) fails with the following (or similar) error:

https://github.com/gtramontina/ooze/actions/runs/4843531326/jobs/8631215763#step:4:26

Error:  panic: failed type checking for file 'internal/cmdtestrunner/cmdtestrunner.go': internal/cmdtestrunner/cmdtestrunner.go:7:2: could not import github.com/gtramontina/ooze/internal/ooze (can't find import: "github.com/gtramontina/ooze/internal/ooze")

goroutine 6 [running]:
testing.tRunner.func1.2({0x6ef2c0, 0xc000202d20})
    /opt/hostedtoolcache/go/1.18.10/x64/src/testing/testing.go:1389 +0x[24](https://github.com/gtramontina/ooze/actions/runs/4843531326/jobs/8631215763#step:4:25)e
testing.tRunner.func1()
    /opt/hostedtoolcache/go/1.18.10/x64/src/testing/testing.go:1392 +0x39f
panic({0x6ef2c0, 0xc000202d20})
    /opt/hostedtoolcache/go/1.18.10/x64/src/runtime/panic.go:838 +0x207
github.com/gtramontina/ooze/internal/gosourcefile.(*GoSourceFile).Incubate(0xc000124bd0, {0x7ab3e0?, 0xc000010078})
    /home/runner/work/ooze/ooze/internal/gosourcefile/gosourcefile.go:46 +0x453
github.com/gtramontina/ooze/internal/ooze.(*Ooze).Release(0xc0001dfe50, {0x95f6e0, 0xe, 0xc0000b7e30?})
    /home/runner/work/ooze/ooze/internal/ooze/ooze.go:83 +0x2[25](https://github.com/gtramontina/ooze/actions/runs/4843531326/jobs/8631215763#step:4:26)
github.com/gtramontina/ooze.Release(0xc000097860, {0xc0000b7f[30](https://github.com/gtramontina/ooze/actions/runs/4843531326/jobs/8631215763#step:4:31), 0x6, 0x3a?})
    /home/runner/work/ooze/ooze/release.go:138 +0xa3a
github.com/gtramontina/ooze_test.TestMutation(0x0?)
    /home/runner/work/ooze/ooze/ooze_mutation_test.go:12 +0xeb
testing.tRunner(0xc000097860, 0x75a558)
    /opt/hostedtoolcache/go/1.18.10/x64/src/testing/testing.go:1439 +0x102
created by testing.(*T).Run
    /opt/hostedtoolcache/go/1.18.10/x64/src/testing/testing.go:1486 +0x[35](https://github.com/gtramontina/ooze/actions/runs/4843531326/jobs/8631215763#step:4:36)f

gtramontina / ooze

Running mutation tests against Ooze itself fails #9