Nil slice vs empty slice. Full article at https://victoronsoftware.com/posts/nil-slice-versus-empty-slice-in-go/

empty_slices.go

package main

/*
According to Go guidelines at https://go.dev/wiki/CodeReviewComments#declaring-empty-slices
When declaring an empty slice, prefer

var t []string

over

t := []string{}

 */

import "fmt"

const usePreference = true
const nullPointer = false

func getEmptySlice() []string {
	if usePreference {
		var slice []string
		return slice
	} else {
		slice := []string{}
		return slice
	}
}

func main() {
	// Sanity check.
	slice := getEmptySlice()
	if slice == nil {
		fmt.Println("Slice is nil.")
	} else {
		fmt.Println("Slice is NOT nil.")
	}
	fmt.Printf("Slice is: %#v\n", slice)

	// Test append.
	slice = append(slice, "bozo")
	fmt.Printf("Test append: %#v\n", slice)

	// Test for loop
	slice = getEmptySlice()
	for range slice {
		fmt.Println("We are in a for loop.")
	}

	// Test len
	fmt.Printf("len: %#v\n", len(slice))

	// Test pass by pointer.
	passByPointer(&slice)
	fmt.Printf("len after passByPointer: %#v\n", len(slice))

	// Test null pointer.
	if nullPointer {
		var nullSlice *[]string
		fmt.Printf("Crash: %#v\n", len(*nullSlice))
	}

}

func passByPointer(slice *[]string) {
	fmt.Printf("passByPointer len: %#v\n", len(*slice))
	*slice = append(*slice, "bozo")
}