How to add a struct to an array of structs in Go - arrays

Question

In golang I'm trying to make an array of messages, and the ability to easily add a new "object" to the array.
type Message struct {
Name string
Content string
}
var Messages = []Message{
{
Name: "Alice",
Content: "Hello Universe",
},{
Name: "Bob",
Content: "Hello World",
},
}
func addMessage(m string) {
var msg = new(Message)
msg.Name = "Carol"
msg.Content = m
Messages = append(Messages, msg)
}
When building I get an error that says:
cannot use msg (type *Message) as type Message in append
Why is append() not working (as I might expect from JavaScript's array.concat()), or is new() not working?
Any other tips on how to improve this code are welcome since I'm obviously new to Go.

Answer 1

Change these 3 lines
var msg = new(Message)
msg.Name = "Carol"
msg.Content = m
to
msg := Message{
Name: "Carol",
Content: m,
}
and everything should work. new creates a pointer to Message. Your slice is not a slice of Message pointers, but a slice of Messages.

Answer 2

In your code, Messages is a slice of Message type, and you are trying to append a pointer of Message type (*Message) to it.
You can fix your program by doing the following:
func addMessage(m string) {
var msg = new(Message) // return a pointer to msg (type *msg)
msg.Name = "Carol"
msg.Content = m
Messages = append(Messages, *msg) // use the value pointed by msg
}
Alternatively, you can declare Messages as a slice of *Message:
var Messages = []*Message{
&Message{ // Now each entry must be an address to a Message struct
Name: "Alice",
Content: "Hello Universe",
},
&Message{
Name: "Bob",
Content: "Hello World",
},
}
In above case, addMessage wouldn't require any changes. But you'll have to modify Messages access everywhere else.