parse go mod to read golang version

pkg/docker/image.go

@@ -5,10 +5,13 @@ package docker
 
 import (
 	"fmt"
+	"os"
+	"path/filepath"
 	"strings"
 
 	"github.com/ava-labs/avalanche-cli/pkg/constants"
 	"github.com/ava-labs/avalanche-cli/pkg/models"
+	"github.com/ava-labs/avalanche-cli/pkg/utils"
 	"github.com/ava-labs/avalanche-cli/pkg/ux"
 )
 
@@ -38,10 +41,34 @@ func parseDockerImageListOutput(output []byte) []string {
 	return strings.Split(string(output), "\n")
 }
 
+func parseRemoteGoModFile(path string, host *models.Host) (string, error) {
+	goMod := filepath.Join(path, "go.mod")
+	// download and parse go.mod
+	tmpFile, err := os.CreateTemp("", "go-mod-*.txt")
+	if err != nil {
+		return "", err
+	}
+	defer os.Remove(tmpFile.Name())
+	if err := host.Download(goMod, tmpFile.Name(), constants.SSHFileOpsTimeout); err != nil {
+		return "", err
+	}
+	return utils.ReadGoVersion(tmpFile.Name())
+}
+
 // BuildDockerImage builds a docker image on a remote host.
 func BuildDockerImage(host *models.Host, image string, path string, dockerfile string) error {
-	_, err := host.Command(fmt.Sprintf("cd %s && docker build -q --build-arg GO_VERSION=%s -t %s -f %s .", path, constants.BuildEnvGolangVersion, image, dockerfile), nil, constants.SSHLongRunningScriptTimeout)
-	return err
+	goVersion, err := parseRemoteGoModFile(path, host)
+	if err != nil {
+		// fall back to default
+		ux.Logger.Info("failed to read go version from go.mod: %s. falling back to default", err)
+		goVersion = constants.BuildEnvGolangVersion
+	}
+	cmd := fmt.Sprintf("cd %s && docker build -q --build-arg GO_VERSION=%s -t %s -f %s .", path, goVersion, image, dockerfile)
+	_, err = host.Command(cmd, nil, constants.SSHLongRunningScriptTimeout)
+	if err != nil {
+		return fmt.Errorf("failed to build docker image %s: %w", image, err)
+	}
+	return nil
 }
 
 // BuildDockerImageFromGitRepo builds a docker image from a git repo on a remote host.
@@ -59,7 +86,7 @@ func BuildDockerImageFromGitRepo(host *models.Host, image string, gitRepo string
 		}
 	}()
 	// clone the repo and checkout commit
-	if _, err := host.Command(fmt.Sprintf("git clone %s %s && cd %s && git checkout %s ", gitRepo, tmpDir, tmpDir, commit), nil, constants.SSHLongRunningScriptTimeout); err != nil {
+	if _, err := host.Command(fmt.Sprintf("git clone %s %s && cd %s && git checkout %s", gitRepo, tmpDir, tmpDir, commit), nil, constants.SSHLongRunningScriptTimeout); err != nil {
 		return err
 	}
 	// build the image

pkg/utils/file.go

@@ -8,6 +8,7 @@ import (
 	"path/filepath"
 
 	"github.com/ava-labs/avalanche-cli/pkg/constants"
+	"golang.org/x/mod/modfile"
 )
 
 func NonEmptyDirectory(dirName string) (bool, error) {
@@ -127,3 +128,19 @@ func GetRemoteComposeServicePath(serviceName string, dirs ...string) string {
 	servicePrefix := filepath.Join(constants.CloudNodeCLIConfigBasePath, "services", serviceName)
 	return filepath.Join(append([]string{servicePrefix}, dirs...)...)
 }
+
+// ReadGoVersion reads the Go version from the go.mod file
+func ReadGoVersion(filePath string) (string, error) {
+	data, err := os.ReadFile(filePath)
+	if err != nil {
+		return "", err
+	}
+	modFile, err := modfile.Parse(filePath, data, nil)
+	if err != nil {
+		return "", err
+	}
+	if modFile.Go != nil {
+		return modFile.Go.Version, nil
+	}
+	return "", fmt.Errorf("go version not found in %s", filePath)
+}

pkg/utils/file_test.go

@@ -44,3 +44,57 @@ func TestExpandHome(t *testing.T) {
 		t.Errorf("ExpandHome failed for empty path: expected %s, got %s", expectedEmptyPath, expandedEmptyPath)
 	}
 }
+
+// createTempGoMod creates a temporary go.mod file with the provided content.
+func createTempGoMod(t *testing.T, content string) string {
+	t.Helper()
+	file, err := os.CreateTemp("", "go.mod")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err := file.Write([]byte(content)); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := file.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	return file.Name()
+}
+
+// TestReadGoVersion tests all scenarios in one function using sub-tests.
+func TestReadGoVersion(t *testing.T) {
+	t.Run("Success", func(t *testing.T) {
+		tempFile := createTempGoMod(t, "module example.com/test\n\ngo 1.23\n")
+		defer os.Remove(tempFile) // Clean up the temp file
+
+		version, err := ReadGoVersion(tempFile)
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+
+		expectedVersion := "1.23"
+		if version != expectedVersion {
+			t.Errorf("expected version %s, got %s", expectedVersion, version)
+		}
+	})
+
+	t.Run("NoVersion", func(t *testing.T) {
+		tempFile := createTempGoMod(t, "module example.com/test\n")
+		defer os.Remove(tempFile)
+
+		_, err := ReadGoVersion(tempFile)
+		if err == nil {
+			t.Fatalf("expected an error, but got none")
+		}
+	})
+
+	t.Run("InvalidFile", func(t *testing.T) {
+		_, err := ReadGoVersion("nonexistent-go.mod")
+		if err == nil {
+			t.Fatalf("expected an error for nonexistent file, but got none")
+		}
+	})
+}