In Go, you can’t directly access the parameters of a function that is passed as an argument. However, you can achieve what you want by modifying the signature of your PaymentProcessor function type to include the context and gateway parameters explicitly, like this:

package main

import (
    "context"
    "log"
)

type PaymentProcessor func(ctx context.Context, gateway string) (bool, error)

func Order(p PaymentProcessor) (string, error) {
    // Access p(ctx) and p(gateway) directly
    ctx := context.TODO() // You might want to use a proper context here
    result, err := p(ctx, "someGateway")
    if err != nil {
        return "", err
    }

    if result {
        return "success", nil
    } else {
        return "failure", nil
    }
}

func MCPaymentProcessor(ctx context.Context, gateway string) (bool, error) {
    // Do something
    return false, nil
}

func main() {
    orderNumber, err := Order(MCPaymentProcessor)
    if err != nil {
        log.Fatalf("failed to process order: %v", err)
    }

    log.Printf("order: %s", orderNumber)
}

Now, when you call p(ctx, "someGateway") inside the Order function, you are passing the context and gateway explicitly to the function, and you can access them directly within the function.