Add error return values to signatures of public methods to allow migr…

…ating to returning errors rather than Fatals in future

lib/install.go

@@ -212,7 +212,7 @@ func InstallLatestImplicitVersion(dryRun bool, requestedVersion, customBinaryPat
 }
 
 // InstallLatestProductImplicitVersion install latest - argument (version) must be provided
-func InstallLatestProductImplicitVersion(product Product, dryRun bool, requestedVersion, customBinaryPath, installPath string, mirrorURL string, preRelease bool) {
+func InstallLatestProductImplicitVersion(product Product, dryRun bool, requestedVersion, customBinaryPath, installPath string, mirrorURL string, preRelease bool) error {
 	_, err := version.NewConstraint(requestedVersion)
 	if err != nil {
 		logger.Errorf("Error parsing constraint %q: %v", requestedVersion, err)
@@ -223,6 +223,7 @@ func InstallLatestProductImplicitVersion(product Product, dryRun bool, requested
 	}
 	logger.Errorf("Error parsing constraint %q: %v", requestedVersion, err)
 	PrintInvalidMinorTFVersion()
+	return nil
 }
 
 // InstallVersion install Terraform product
@@ -234,7 +235,7 @@ func InstallVersion(dryRun bool, version, customBinaryPath, installPath, mirrorU
 }
 
 // InstallProductVersion install with provided version as argument
-func InstallProductVersion(product Product, dryRun bool, version, customBinaryPath, installPath, mirrorURL string) {
+func InstallProductVersion(product Product, dryRun bool, version, customBinaryPath, installPath, mirrorURL string) error {
 	logger.Debugf("Install version %s. Dry run: %s", version, strconv.FormatBool(dryRun))
 	if !dryRun {
 		if validVersionFormat(version) {
@@ -248,7 +249,7 @@ func InstallProductVersion(product Product, dryRun bool, version, customBinaryPa
 				ChangeProductSymlink(product, installFileVersionPath, customBinaryPath)
 				logger.Infof("Switched %s to version %q", product.GetName(), requestedVersion)
 				addRecent(requestedVersion, installPath, product) //add to recent file for faster lookup
-				return
+				return nil
 			}
 
 			// If the requested version had not been downloaded before
@@ -268,6 +269,7 @@ func InstallProductVersion(product Product, dryRun bool, version, customBinaryPa
 			os.Exit(1)
 		}
 	}
+	return nil
 }
 
 // InstallProductOption displays & installs tf version
@@ -288,7 +290,7 @@ type VersionSelector struct {
 // InstallProductOption displays & installs tf version
 /* listAll = true - all versions including beta and rc will be displayed */
 /* listAll = false - only official stable release are displayed */
-func InstallProductOption(product Product, listAll, dryRun bool, customBinaryPath, installPath string, mirrorURL string) {
+func InstallProductOption(product Product, listAll, dryRun bool, customBinaryPath, installPath string, mirrorURL string) error {
 	var selectVersions []VersionSelector
 
 	var versionMap map[string]bool = make(map[string]bool)
@@ -347,4 +349,5 @@ func InstallProductOption(product Product, listAll, dryRun bool, customBinaryPat
 		install(product, selectVersions[selectedItx].Version, customBinaryPath, installPath, mirrorURL)
 	}
 	os.Exit(0)
+	return nil
 }