Fun fact: `go run .` was retrofitted on after `go run main.go` because go run was initially designed to only accept explicit filenames as an argument [1]. I can't imagine how people used to use `go run` without the ability to specify whole packages (globs don't work well because it includes test files as well).

> Potential design based on discussion with proposal review:

> go run [go flags] [single-package-or-*.go-list] [subprocess flags]

before that it was just

> go run [go flags] [*.go-list] [subprocess flags]

[1] https://github.com/golang/go/issues/22726