hash/crc64: use t.Fatalf in TestGolden

Use t.Fatalf instead of t.Errorf followed by t.FailNow.

Change-Id: Ie31f8006e7d9daca7f59bf6f0d5ae688222be486
Reviewed-on: https://go-review.googlesource.com/c/144111
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/hash/crc64/crc64_test.go

@@ -62,15 +62,13 @@ func TestGolden(t *testing.T) {
 		io.WriteString(c, g.in)
 		s := c.Sum64()
 		if s != g.outISO {
-			t.Errorf("ISO crc64(%s) = 0x%x want 0x%x", g.in, s, g.outISO)
-			t.FailNow()
+			t.Fatalf("ISO crc64(%s) = 0x%x want 0x%x", g.in, s, g.outISO)
 		}
 		c = New(tabECMA)
 		io.WriteString(c, g.in)
 		s = c.Sum64()
 		if s != g.outECMA {
-			t.Errorf("ECMA crc64(%s) = 0x%x want 0x%x", g.in, s, g.outECMA)
-			t.FailNow()
+			t.Fatalf("ECMA crc64(%s) = 0x%x want 0x%x", g.in, s, g.outECMA)
 		}
 	}
 }