staticcheck: flag TestMain functions that don't call m.Run

[jacob2964]

Without the os.Exit(m.Run()) line in the TestMain function, control is never passed to the tests and TestMain is the only thing that runs. It can lead to tests appearing to pass when they never actually ran. The TestSanity test "passes" below:

package main_test

import (
	"testing"

	"github.com/stretchr/testify/assert"
)

func TestMain(m *testing.M) {
}

func TestSanity(t *testing.T) {
	assert.Equal(t, 1, 0)
}

It would be nice if there was a linting warning letting the developer know that not having this line could cause unexpected behavior.

[abitrolly]

Fixed? golang/go@2f54081

[dominikh]

This issue is more about the lack of a call to m.Run than a call to os.Exit.

[ccoVeille]

call to os.Exit.

For anyone interested by detecting os.Exit call in TestMain

This PR is about it

mgechev/revive#1208

[ccoVeille]

This issue is more about the lack of a call to m.Run

To make it clear, I agree we should have something to detect this