add golangci-lint linter (#5499)

plugin/header/header_test.go

@@ -78,7 +78,5 @@ func TestHeader(t *testing.T) {
 			t.Errorf("Test %d: Expected flag state=%t, but got %t", i, test.expected, test.got(m))
 			continue
 		}
-
 	}
-
 }

plugin/header/setup.go

@@ -46,5 +46,4 @@ func parse(c *caddy.Controller) ([]Rule, error) {
 		}
 	}
 	return nil, c.ArgErr()
-
 }