Exported functions from another package

Question

I am following instructions in https://golang.org/doc/code.html#Workspaces link and I build my first Go program.

So, I tried to make library with this instruction = https://golang.org/doc/code.html#Library

and everything is perfect until building hello.go, its gives me this error.

/hello.go:10:13: undefined: stringutil.Reverse

I've already rebuild my reverse.go.

Thats my code:

package main

import (
    "fmt"

    "github.com/d35k/stringutil"
)

func main() {
    fmt.Printf(stringutil.Reverse("!oG ,olleH"))
}

that's my reverse.go (same as docs)

package stringutil

func reverse(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)
}

and my gopath variable

export GOPATH=$HOME/GoLang

and my files ar in

GoLang/src/github.com/mygithubusername/

Answer 1

Golang Tour specify exported name as

A name is exported if it begins with a capital letter. And When importing a package, you can refer only to its exported names. Any "unexported" names are not accessible from outside the package.

Change the name of reverse func to Reverse to make it exportable to main package. Like below

package stringutil

func Reverse(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)
}