EnvVar middleware for Fiber exposes environment variables with configurable options.
Mount the middleware on a path; it cannot be used without one.
Signatures
func New(config ...Config) fiber.Handler
Usage
import (
"github.com/gofiber/fiber/v3"
"github.com/gofiber/fiber/v3/middleware/envvar"
)
Basic Example
// Initialize default config (exports no variables)
app.Use("/expose/envvars", envvar.New())
// Or extend your config for customization
app.Use("/expose/envvars", envvar.New(
envvar.Config{
ExportVars: map[string]string{"testKey": "", "testDefaultKey": "testDefaultVal"},
}),
)
{
"vars": {
"testKey": "testValue",
"testDefaultKey": "testDefaultVal"
}
}
Expose Specific Variables
app.Use("/env", envvar.New(envvar.Config{
ExportVars: map[string]string{
"APP_ENV": "",
"APP_VERSION": "1.0.0", // Default value if not set
"DEBUG_MODE": "false",
},
}))
Configuration
ExportVars
map[string]string
default:"nil"
Lists the environment variables to expose. The key is the environment variable name, and the value is the default value to use if the variable is not set.
Default Config
Config{}
// Exports no environment variables
Common Use Cases
Health Check Endpoint with Version Info
app.Use("/health", envvar.New(envvar.Config{
ExportVars: map[string]string{
"APP_VERSION": "unknown",
"BUILD_TIME": "unknown",
"GIT_COMMIT": "unknown",
},
}))
Development Environment Info
if os.Getenv("ENV") == "development" {
app.Use("/debug/env", envvar.New(envvar.Config{
ExportVars: map[string]string{
"GO_VERSION": "",
"GOARCH": "",
"GOOS": "",
"DATABASE_URL": "hidden", // Don't expose actual value
},
}))
}
Feature Flags
app.Use("/api/features", envvar.New(envvar.Config{
ExportVars: map[string]string{
"FEATURE_NEW_UI": "false",
"FEATURE_BETA_ACCESS": "false",
"FEATURE_ANALYTICS": "true",
},
}))
Configuration Discovery
app.Use("/config", envvar.New(envvar.Config{
ExportVars: map[string]string{
"API_TIMEOUT": "30",
"MAX_UPLOAD_SIZE": "10485760",
"RATE_LIMIT": "100",
},
}))
Security Considerations
Never expose sensitive information:
- Do not expose actual database passwords, API keys, or secrets
- Use this middleware only for non-sensitive configuration
- Protect the endpoint with authentication in production
- Consider IP whitelisting for sensitive environments
Protected Endpoint Example
// Only accessible from localhost
app.Use("/internal/env", func(c fiber.Ctx) error {
if c.IP() != "127.0.0.1" {
return c.SendStatus(fiber.StatusForbidden)
}
return c.Next()
})
app.Use("/internal/env", envvar.New(envvar.Config{
ExportVars: map[string]string{
"APP_ENV": "",
"APP_VERSION": "",
},
}))