feat: Add capability to set default for environment variable in config (#1248)

Support `${ENV_VALUE:default_value}`

🛠️ Fixes #1001

cmd/root.go

@@ -265,8 +265,9 @@ type ToolsFile struct {
 }
 
 // parseEnv replaces environment variables ${ENV_NAME} with their values.
+// also support ${ENV_NAME:default_value}.
 func parseEnv(input string) (string, error) {
-	re := regexp.MustCompile(`\$\{(\w+)\}`)
+	re := regexp.MustCompile(`\$\{(\w+)(:(\w+))?\}`)
 
 	var err error
 	output := re.ReplaceAllStringFunc(input, func(match string) string {
@@ -277,6 +278,9 @@ func parseEnv(input string) (string, error) {
 		if value, found := os.LookupEnv(variableName); found {
 			return value
 		}
+		if len(parts) == 4 {
+			return parts[3]
+		}
 		err = fmt.Errorf("environment variable not found: %q", variableName)
 		return ""
 	})

docs/en/getting-started/configure.md

@@ -22,6 +22,11 @@ etc., you could use environment variables instead with the format `${ENV_NAME}`.
   user: ${USER_NAME}
   password: ${PASSWORD}
 ```
+A default value can be specified like `${ENV_NAME:default}`.
+
+```yaml
+  port: ${DB_PORT:3306}
+```
 
 ### Sources