Function in same package undefined

Question

My project structure is like this.

packagetest/
    main.go
    lib.go

In main.go, I have this code.

package m         


        

Answer 1

On the golang.org webpage you can read about the build command that:

If the arguments are a list of .go files, build treats them as a list of source files specifying a single package.

So, go build main.go will treat main.go as a single package. Instead, you should use:

go build

to include all files in the folder.