Go Academy · Lesson

Auth and Rate Limiting Middleware

JWT validation and token bucket rate limiting

JWT auth middleware

Extract, parse, and validate a JWT from the Authorization header:

func JWTAuth(secret []byte) func(http.Handler) http.Handler {
    return func(next http.Handler) http.Handler {
        return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            header := r.Header.Get("Authorization")
            if !strings.HasPrefix(header, "Bearer ") {
                http.Error(w, "missing token", 401); return
            }
            token := strings.TrimPrefix(header, "Bearer ")
            claims, err := parseJWT(token, secret)
            if err != nil {
                http.Error(w, "invalid token", 401); return
            }
            ctx := context.WithValue(r.Context(), claimsKey{}, claims)
            next.ServeHTTP(w, r.WithContext(ctx))
        })
    }
}

API key auth

Validate an API key from a header against a database or in-memory set:

func APIKeyAuth(validKeys map[string]bool) func(http.Handler) http.Handler {
    return func(next http.Handler) http.Handler {
        return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            key := r.Header.Get("X-API-Key")
            if !validKeys[key] {
                http.Error(w, "forbidden", 403); return
            }
            next.ServeHTTP(w, r)
        })
    }
}

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