Why does Go throw Undefined for a struct declared in the same package?

Question

go

Good afternoon, comrades! I'm doing a small project on Go, until recently it was going well, but for some reason in the following case it began to give an error:
The main.go file contains the following code:

package main

func main() {
  var m = Message{
    Type: "LOL",
  }
  println(m.Type)
}

The msg.go file contains the following code:

package main

// Message - test message
type Message struct {
  Type string
}

When running the command

go run main.go

Gives an error message:

.\main.go:4:10: undefined: Message

Why is that? Previously, everything worked fine in this case.

Answer 1

Because you are only running one main.go file. Either run all *.go, or write the names of 2 files - go run main.go msg.go.