Fix compilation for non-modules (cucumber#436)

CHANGELOG.md

@@ -8,6 +8,12 @@ This document is formatted according to the principles of [Keep A CHANGELOG](htt
 
 ---
 
+## [v0.12.2]
+
+### Fixed
+
+- Error in `go mod tidy` with `GO111MODULE=off` ([436]((https://github.com/cucumber/godog/pull/436) - [vearutop])
+
 ## [v0.12.1]
 
 ### Fixed
@@ -196,6 +202,7 @@ This document is formatted according to the principles of [Keep A CHANGELOG](htt
 
 <!-- Releases -->
 
+[v0.12.2]: https://github.com/cucumber/godog/compare/v0.12.1...v0.12.2
 [v0.12.1]: https://github.com/cucumber/godog/compare/v0.12.0...v0.12.1
 [v0.12.0]: https://github.com/cucumber/godog/compare/v0.11.0...v0.12.0
 [v0.11.0]: https://github.com/cucumber/godog/compare/v0.10.0...v0.11.0

internal/builder/builder.go

@@ -127,9 +127,11 @@ func Build(bin string) error {
 	// we also print back the temp WORK directory
 	// go has built. We will reuse it for our suite workdir.
 	temp := fmt.Sprintf(filepath.Join("%s", "temp-%d.test"), os.TempDir(), time.Now().UnixNano())
-	modTidyOutput, err := exec.Command("go", "mod", "tidy").CombinedOutput()
-	if err != nil {
-		return fmt.Errorf("failed to tidy modules in tested package: %s, reason: %v, output: %s", abs, err, string(modTidyOutput))
+	if os.Getenv("GO111MODULE") != "off" {
+		modTidyOutput, err := exec.Command("go", "mod", "tidy").CombinedOutput()
+		if err != nil {
+			return fmt.Errorf("failed to tidy modules in tested package: %s, reason: %v, output: %s", abs, err, string(modTidyOutput))
+		}
 	}
 	testOutput, err := exec.Command("go", "test", "-c", "-work", "-o", temp).CombinedOutput()
 	if err != nil {