I can't verify requests for Discord interactions URL properly

[preslavmihaylov]

I'm trying to write a golang handler, which reacts to discord interactions. I've set it up as the interactions URL in my discord developer portal.

This is the code I've written:

var secrets struct {
	DiscordPublicKey string
}

type UnknownDiscordInteraction struct {
	InteractionType discordgo.InteractionType `json:"type"`
}

func DiscordWebhook(w http.ResponseWriter, r *http.Request) {
	body, err := io.ReadAll(r.Body)
	if err != nil {
		http.Error(w, "Error reading request body", http.StatusInternalServerError)
		return
	}

	publicKeyBytes, err := hex.DecodeString(secrets.DiscordPublicKey)
	if err != nil {
		http.Error(w, "Error decoding hex string", http.StatusInternalServerError)
		return
	}

	if !discordgo.VerifyInteraction(r, publicKeyBytes) {
		http.Error(w, "invalid request signature", http.StatusUnauthorized)
		return
	}

	var interaction UnknownDiscordInteraction
	if err := json.Unmarshal(body, &interaction); err != nil {
		http.Error(w, "Error unmarshalling request body", http.StatusInternalServerError)
		return
	}

	if interaction.InteractionType == discordgo.InteractionPing {
		pongResp, err := json.Marshal(discordgo.InteractionResponse{
			Type: discordgo.InteractionResponsePong,
		})
		if err != nil {
			http.Error(w, "Error marshalling response", http.StatusInternalServerError)
			return
		}

		// set content-type header
		w.Header().Set("Content-Type", "application/json")
		w.Write(pongResp)
		w.WriteHeader(http.StatusOK)
		return
	}

	w.WriteHeader(http.StatusOK)
}

I can't save the endpoint in the developer dashboard, because any challenge request that discord sends I fail to verify, it returns that the request is invalid.

I am passing the DiscordPublicKey as a string, copied from my discord developer dashboard. Anyone has a clue what I'm doing wrong?