Interface/API Design Question

base.go

package email

import (
	"context"
)

// Version 1

// Sender is an interface to hide the fact we're using a 3rd party library
type Sender interface {
	// NewMessage sets up a basic email message that's ready to send
	NewMessage(sender, subject, body, recipient string) *MessageImpl
	// Send attempts to send the email -- if successful returns a human-readable status message & a message ID
	Send(context.Context, Message) (string, string, error)
}

type Message interface {
	AddAttachment(string)
}


// VS

// Version 2

type Sender interface {
	NewMessage(sender, subject, body, recipient string) *MessageImpl
}

type Message interface {
	AddAttachment(string)
	Send(context.Context) (string,string, error)
}