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

Run all the file then able to call

go run *.go

or

go run main.go lib.go

Answer 2

If using multiple files for Go main pkg, instead of single file path as go run main.go, go require main pkg dir in the run or build command, like:

#from outside packagetest dir
go run ./packagetest/
go build ./packagetest/

#from within packagetest:
go run ./
go build ./

Answer 3

This problem will happen when go cannot find your other file (like lib.go in this example).

If you use JetBrains Goland , you should change your "Run kind" to "Directory". Goland will help you to do these:

• go build .
• run this execution file.

---

If you use JetBrains Goland , you can contrast the difference between "Run kind".

When i select "File", and then run, you will see the message on the console, like this:

GOROOT=C:\Go #gosetup
GOPATH=C:\Users\hgs\go #gosetup
C:\Go\bin\go.exe build -o C:\Users\hgs\AppData\Local\Temp\___go_build_select_go__4_.exe "C:/Users/hgs/Google Drive/My Maps/computer/2.programming_lang/Golang/source-code-refer/basic/select.go" #gosetup
# command-line-arguments
.\select.go:14:16: undefined: Add

When you select "Directory" and select your directory, and then run, you will see something like this:

GOROOT=C:\Go #gosetup
GOPATH=C:\Users\hgs\go #gosetup
C:\Go\bin\go.exe build -o C:\Users\hgs\AppData\Local\Temp\___go_build_basic_.exe . #gosetup
C:\Users\hgs\AppData\Local\Temp\___go_build_basic_.exe #gosetup
...