Unexpected behaviour of slices, when passed as argument in a function and mutated

go-slices-as-param.go

package main

import (
	"fmt"
)

func sliceExtender(sl []int) {
	sl = append(sl, 33)
	sl[0] = 5
	fmt.Printf("len %d, cap %d, sliceOne[0]=%d, added last elemnt =%d \n", len(sl), cap(sl), sl[0], sl[len(sl)-1])
}
func main() {
	sliceOne := make([]int, 1, 10)
	sliceOne[0] = 1
	fmt.Println("SliceOne created")
	fmt.Printf("len %d, cap %d, sliceOne[0]=%d \n", len(sliceOne), cap(sliceOne), sliceOne[0])
	fmt.Println("SliceOne in function")
	sliceExtender(sliceOne)
	fmt.Println("SliceOne in main")
	fmt.Printf("len %d, cap %d, sliceOne[0]=%d, added last elemnt =%d \n", len(sliceOne), cap(sliceOne), sliceOne[0], sliceOne[len(sliceOne)-1])

	fmt.Println("--------------------------------------------------")
	sliceTwo := make([]int, 10)
	sliceTwo[0] = 1
	fmt.Println("SliceTwo created")
	fmt.Printf("len %d, cap %d, SliceTwo[0]=%d \n", len(sliceTwo), cap(sliceTwo), sliceTwo[0])
	fmt.Println("SliceTwo in function")
	sliceExtender(sliceTwo)
	fmt.Println("SliceTwo in main")
	fmt.Printf("len %d, cap %d, SliceTwo[0]=%d, added last elemnt =%d \n", len(sliceTwo), cap(sliceTwo), sliceTwo[0], sliceTwo[len(sliceTwo)-1])

}