> ## Documentation Index > Fetch the complete documentation index at: https://openrouter.ai/docs/llms.txt > Use this file to discover all available pages before exploring further. # ExchangeAuthCodeForAPIKeyCodeChallengeMethod The method used to generate the code challenge ## Example Usage ```go theme={null} import ( "github.com/OpenRouterTeam/go-sdk/models/operations" ) value := operations.ExchangeAuthCodeForAPIKeyCodeChallengeMethodS256 // Open enum: custom values can be created with a direct type cast custom := operations.ExchangeAuthCodeForAPIKeyCodeChallengeMethod("custom_value") ``` ## Values | Name | Value | | --------------------------------------------------- | ----- | | `ExchangeAuthCodeForAPIKeyCodeChallengeMethodS256` | S256 | | `ExchangeAuthCodeForAPIKeyCodeChallengeMethodPlain` | plain |