Make go-version-file: go.mod the default

[andig]

Description:
Currently, I have to add

with:
  go-version-file: go.mod

for all builds to specify a go version. Instead, the "default" go version that any go program would use is the one from the go.mod with fallback to the installed go version. This should be the default for setup-go, too.

Justification:
Simplify developer's life.

Are you willing to submit a PR?

[mahalakshmi-rekadi]

Hi, @andig 👋 Thank you for the feature request, we will investigate it and get back to you as soon as we have some feedback.