Hello world in Goland - go

Question

I'm following the official Go tutorial: https://golang.org/doc/code.html
But instead of doing things via the command line I'm using GoLand. I'm able to run the program and see "Hello World" printed when everything is contained inside the HelloWorld.go package, but when I add the morestrings package and try to import it in HelloWorld.go I get an import error (Cannot resolve file 'morestrings'):
package main
import (
"morestrings"
"fmt"
)
func main() {
fmt.Println(morestrings.ReverseRunes("!oG ,olleH"))
}
Here's what I've defined the morestrings package to be:
package morestrings
// ReverseRunes returns its argument string reversed rune-wise left to right.
func ReverseRunes(s string) string {
r := []rune(s)
for i, j := 0, len(r)-1; i < len(r)/2; i, j = i+1, j-1 {
r[i], r[j] = r[j], r[i]
}
return string(r)
}
I've set the GOPATH in project settings to the root directory of my project (GoGoHelloWorld). My understanding is that Go will look for imports starting at GOPATH, so I would expect it to find the morestrings package. Here's the file structure:

Answer 1

First, I think you can take a look at this go project layout which may diffs with other language like C++ or Java.
Second, I would like using go module.

Answer 2

If your go path is GOPATH=/Users/.../IdeaProjects/FinalGoHelloWorld.
I am assuming you have created a project "GoGoHelloWorld" inside "FinalGoHelloWorld".
Your import statement is wrong, you should use "GoGoHelloWorld/src/morestrings"

Answer 3

When you try to import a package in GO, it doesn't look for that package everywhere in the whole file system, it looks for that package in specific folders.
These folders are the src folder inside your GOROOT and GOPATH directory.
All your code should be place inside this GOPATH's src folder.
You mentioned in the comments section GOPATH=/Users/.../IdeaProjects/FinalGoHelloWorld. So you must create a src folder inside this directory and all the code goes inside src.
So your GoGoHelloWorld folder's full path must be /Users/.../IdeaProject/FinalGoHelloWorld/src/GoGoHelloWorld, so now your import should look more like
import (
"GoGoHelloWorld/src/morestrings"
"fmt"
)
For reference, since your GOROOT is GOROOT=/usr/local/go your fmt package(folder) will be loacted at /usr/local/go/src/fmt
I would also recommend changing the GOPATH folder name from FinalGoHelloWorld to something more generic like GoWorkspace. So inside GoWorkspace/src you could create multiple projects folders with specific name.
One last thing, create two more folders, bin and pkg, along with srcinside GOPATH