func stdNowSeqFunc(seq []int64) func() time.Time {
	var i int
	return func() time.Time {
		defer func() { i++ }()
		return time.Unix(0, seq[i])
	}
}
Returns a time.Now-like function that walks seq returning time.Unix(0,
seq[i]) in successive calls.
package missinggo
import (
	"testing"
	"time"
	"github.com/stretchr/testify/assert"
)
func withCustomStdNow(stdNow func() time.Time, suite func()) {
	oldStdNow := stdNowFunc
	oldSkew := monotonicSkew
	defer func() {
		stdNowFunc = oldStdNow
		monotonicSkew = oldSkew
	}()
	stdNowFunc = stdNow
	suite()
}