How to call a function from another file in Go: project structure and import

Hello, colleagues! I just started learning Go and encountered a problem that seems very simple to me, but I can't find the right solution. I have two files in one project: `main.go` and `helpers.go`. In `helpers.go`, I declared a function `sayHello()` that prints a greeting. In `main.go`, I'm trying to call this function, but the compiler complains that the function is not defined. Here is my folder structure: ``` myproject/ ├── main.go └── helpers.go ``` Code for `helpers.go`: ```go package main import "fmt" func sayHello() { fmt.Println("Hello from helpers!") } ``` Code for `main.go`: ```go package main func main() { sayHello() } ``` When I run `go run main.go`, I get an error: `undefined: sayHello`. If I run `go run main.go helpers.go`, then it