Echo middlewares

In this brief article, I aim to highlight an ideal use-case for middleware, shedding light on its functionality and practical implementation.

Middleware serves as a crucial intermediary between user requests and application logic. In the following example, I'll demonstrate how middleware can authenticate users and seamlessly pass custom context to a micro-service, streamlining the authentication process without burdening the service with additional authentication logic.

Let's Dive into the Code

Creating a custom context is straightforward. We begin by defining a new structure that embeds echo.Context, ensuring seamless implementation of the Context interface. While exporting only userID could suffice, embedding echo.Context offers flexibility and avoids potential conflicts.

type UserContext struct {
    echo.Context
    userID int64
}

func (c *UserContext) GetUserID() int64 {
    return c.userID
}

Next, we implement the Middleware function, which retrieves and returns HandlerFunc, adhering to the standard middleware pattern in Echo.

type (
  MiddlewareFunc func(HandlerFunc) HandlerFunc
  HandlerFunc func(Context) error
)

Here's how we implement the middleware function, requiring an authenticator to perform the actual authentication.

type authenticator interface {
    AuthenticateUser(ctx context.Context, token string) (int64, error)
}

func AuthenticateUserMiddleware(authenticator authenticator) echo.MiddlewareFunc {
    return func(next echo.HandlerFunc) echo.HandlerFunc {
        return func(c echo.Context) error {
            // Retrieve token from the request
            authToken := c.Request().Header.Get("Authorization")
            if authToken == "" {
                return echo.NewHTTPError(http.StatusUnauthorized, "No authorization token")
            }

            // Authenticate the user and retrieve the user ID
            userID, err := authenticator.AuthenticateUser(c.Request().Context(), authToken)
            if err != nil {
                return echo.NewHTTPError(http.StatusUnauthorized, "Invalid authorization token")
            }

            // Create a new custom context
            uctx := &UserContext{
                Context: c,
                userID:  userID,
            }

            // Pass the new context forward
            return next(uctx)
        }
    }
}

How to use this middleware and custom Context

You can easily incorporate this middleware into your routes for GET/POST requests.

echo := echox.CreateEchoServer()
echo.GET("/:id", func(c echo.Context) error {
    return s.getRecipe(c)
}, AuthenticateUserMiddleware(s.authenticator))

To utilize the custom context, type casting is necessary along with validation.

func (s recipe) getRecipe(c echo.Context) error {
    uc, isOk := c.(*echox.UserContext)
    if !isOk {
        return echo.NewHTTPError(http.StatusInternalServerError, "wrong context type")
    }

    userID := uc.GetUserID()
    ...
}

Summary

Middleware proves to be an invaluable tool, simplifying complex tasks such as authentication. I hope this article provides you with a deeper understanding of middleware functionality and how to implement it effectively.

Echo middlewares

Let's Dive into the Code

How to use this middleware and custom Context

Summary

Further Reading

Bonus Trivia