将本地包导入另一个文件夹

I keep getting the following error and I have been trying out some of the other suggestions in other Stack Overflow threads.

./main.go:15:13: undefined: checkEnv

Folder Structure:

├── README.md
├── main.go
└── validate
    └── args.go

$GOPATH

/Users/myusername/go

main.go

package main

import (
    "fmt"
    "log"
    "os"

    "projectName/validate"

    "gopkg.in/urfave/cli.v1"
)

func main() {
    app := cli.NewApp()
    app.Name = "thirsty"
    app.Action = func(c *cli.Context) error {
        result := checkEnv(c.Args().Get(0))

        fmt.Println(result)
        return nil
    }
    err := app.Run(os.Args)

    if err != nil {
        log.Fatal(err)
    }

}

validate/args.go

package validate

import "strings"

func checkEnv(environment string) bool {
    env := strings.ToLower(environment)
    return env != "qa" && env != "dev"
}

My project is in the src directory of my $GOPATH. If this is not the proper way to do code splitting, is there a generally used convention to follow?

Any feedback appreciated.

There are two problems here.

1. The checkEnv method is not exported [in validate/args.go]. ie it is usable only inside the same package and not other packages
   To export just capitalize the first letter of the method CheckEnv. Now CheckEnv can be used from other packages

2. While calling a method from other package, the syntax should be packagename.ExportedMethod(params...).
   so in your code [in main.go] it should be result := validate.CheckEnv(c.Args().Get(0))