func (o *OAuthService) BuildAuthorizationURL(ctx context.Context, params *AuthorizationURLParams) (*AuthorizationURL, error)

result, err := client.OAuth.BuildAuthorizationURL(ctx, &avnologyid.AuthorizationURLParams{
    Scopes:      []string{"openid", "profile", "email", "offline_access"},
    RedirectURI: "https://myapp.com/callback",
})
if err != nil {
    log.Fatal(err)
}

fmt.Println("Redirect to:", result.URL)
// Store code verifier in session for the callback
session.Set("code_verifier", result.CodeVerifier)
session.Set("oauth_state", result.State)

tokens, err := client.OAuth.ExchangeCode(ctx, &avnologyid.ExchangeCodeParams{
    Code:         authCode,
    CodeVerifier: codeVerifier,
    RedirectURI:  "https://myapp.com/callback",
})
if err != nil {
    var invalidGrant *errors.InvalidGrantError
    if errors.As(err, &invalidGrant) {
        log.Println("Authorization code expired or invalid")
        return
    }
    log.Fatal(err)
}

fmt.Println("Access token:", tokens.AccessToken)
fmt.Println("Refresh token:", tokens.RefreshToken)
fmt.Println("Expires in:", tokens.ExpiresIn, "seconds")

func callbackHandler(w http.ResponseWriter, r *http.Request) {
    code := r.URL.Query().Get("code")
    state := r.URL.Query().Get("state")

    // Validate state
    savedState := getSession(r).Get("oauth_state")
    if state != savedState {
        http.Error(w, "State mismatch", http.StatusBadRequest)
        return
    }

    codeVerifier := getSession(r).Get("code_verifier")

    tokens, err := client.OAuth.ExchangeCode(r.Context(), &avnologyid.ExchangeCodeParams{
        Code:         code,
        CodeVerifier: codeVerifier,
        RedirectURI:  "https://myapp.com/callback",
    })
    if err != nil {
        http.Error(w, "Token exchange failed", http.StatusInternalServerError)
        return
    }

    // Store tokens in session
    session := getSession(r)
    session.Set("access_token", tokens.AccessToken)
    session.Set("refresh_token", tokens.RefreshToken)
    session.Save(w)

    http.Redirect(w, r, "/dashboard", http.StatusFound)
}