Can a Go Project Have Both a Library and a CLI in the Same Directory?

Can Two Packages Reside in the Same Directory?

When developing projects requiring both a library and command-line interface (CLI), it's common to encounter conflicts between two packages existing in the same directory. Due to the Go compiler's requirement for a package named "main" with a "func main" as the entry point, it's thought to be impossible to have separate packages for both the library and CLI.

Solution: Nested Package Structure

However, there is a workaround to this issue by moving both packages into a new folder within the same directory as the "main.go" file. The key is to ensure the new package is imported from the correct path within "$GOPATH".

Example:

Consider the updated directory structure:

whatever.io/
    myproject/
        a/                # New folder
            a.go
        main.go

In "main.go", import the new package from its nested path:

package main

import (
    "../myproject/a"
)

func main() {
    a.Hello()
}

In "a.go", define functions for the library:

package a

import (
    "fmt"
)

func Hello() {
    fmt.Println("hello from a")
}

Building and Running:

Now, you can build and run the project successfully:

go run main.go
# Prints "hello from a"

go build
# Creates the executable without errors

This solution allows you to have both a library (package "a") and CLI (package "main") in the same directory, resolving the conflict caused by having two packages with the same name in the same directory.

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