Linked list of integers https://goplay.space/#jOlr7VSOmrK

list.go

package main

import (
	"errors"
	"fmt"
)

type node struct {
	value int
	next  *node
}

type list struct {
	length int
	head   *node
	tail   *node
}

type List interface {
	Print()
	Length() int
	IndexOf(value int) int
	Append(value int)
	Insert(value, position int) error
	Remove(position int) error
}

var _ List = &list{}

func NewList() List {
	return &list{}
}

func newNode(value int) *node {
	return &node{value, nil}
}

func (l *list) insertFirst(value int) error {
	if l.head == nil {
		return errors.New("Head list cannot be nil")
	}

	node := newNode(value)
	node.next = l.head
	l.head = node
	l.length += 1

	return nil
}

func (l *list) insertBetween(value, position int) error {
	current := l.head

	for index := 0; index < position-1; index++ {
		if current == nil {
			return errors.New("Position does not exist")
		}

		current = current.next
	}

	node := newNode(value)
	node.next = current.next
	current.next = node
	l.length += 1

	return nil
}

func (l *list) insertLast(value int) error {
	if l.tail == nil {
		return errors.New("Tail list cannot be nil")
	}

	node := newNode(value)
	l.tail.next = node
	l.tail = node
	l.length += 1

	return nil
}

func (l *list) removeFirst() error {
	if l.head == nil {
		return errors.New("Head list cannot be nil")
	}

	l.head = l.head.next
	l.length -= 1

	return nil
}

func (l *list) removeBetween(position int) error {
	current := l.head

	for index := 0; index < position-1; index++ {
		if current == nil {
			return errors.New("Position does not exist")
		}

		current = current.next
	}

	current.next = current.next.next
	l.length -= 1

	return nil
}

func (l *list) removeLast() error {
	if l.head == nil {
		return errors.New("Head list cannot be nil")
	}

	if l.tail == nil {
		return errors.New("Tail list cannot be nil")
	}

	current := l.head
	for ; current.next != l.tail; current = current.next {
	}
	current.next = nil
	l.length -= 1

	return nil
}

func (l *list) Append(value int) {
	_ = l.Insert(value, l.length)
}

func (l *list) Insert(value, position int) error {
	if position > l.length {
		return errors.New("Position is greater than length")
	}

	if position < 0 {
		return errors.New("Position is lower than 0")
	}

	if l.head == nil && l.tail == nil {
		node := newNode(value)
		l.head = node
		l.tail = node
		l.length += 1
		return nil
	}

	if position == 0 {
		return l.insertFirst(value)
	}

	if position == l.length {
		return l.insertLast(value)
	}

	return l.insertBetween(value, position)
}

func (l *list) Remove(position int) error {
	if l.length == 0 {
		return errors.New("Empty list")
	}

	if l.length < position {
		return errors.New("Position is greater than length")
	}

	if l.head == l.tail {
		l.head = nil
		l.tail = nil
		l.length -= 1
		return nil
	}

	if position == 0 {
		return l.removeFirst()
	}

	if position == l.length {
		return l.removeLast()
	}

	return l.removeBetween(position)
}

// Search looks for the given number in the list and returns the
// position in case it exists. Otherwise, returns -1
func (l *list) IndexOf(value int) int {
	index := 0

	for current := l.head; current != nil; current = current.next {
		if current.value == value {
			return index
		}

		index += 1
	}

	return -1
}

func (l *list) Print() {
	for current := l.head; current != nil; current = current.next {
		fmt.Printf("%d ", current.value)
	}

	fmt.Println()
}

// Length returns the length of the list
func (l *list) Length() int {
	return l.length
}

func main() {
	list := NewList()

	list.Append(11)
	list.Print()
	list.Append(12)
	list.Print()
	list.Append(13)
	list.Print()

	list = NewList()

	// Insert in empty list
	err := list.Insert(11, 0)
	fmt.Println(err)
	list.Print()

	// Insert in inexistent position
	err = list.Insert(11, 2)
	fmt.Println(err)
	list.Print()

	// Insert at the end
	err = list.Insert(13, 1)
	fmt.Println(err)
	list.Print()

	// Insert in between
	err = list.Insert(12, 1)
	fmt.Println(err)
	list.Print()

	// Insert at the begining
	err = list.Insert(10, 0)
	fmt.Println(err)
	list.Print()

	// IndexOf
	fmt.Println(list.IndexOf(11))

	// Remove first
	err = list.Remove(0)
	fmt.Println(err)
	list.Print()

	// Remove between
	err = list.Remove(1)
	fmt.Println(err)
	list.Print()

	// Remove last
	err = list.Remove(1)
	fmt.Println(err)
	list.Print()

	// Remove inexistent position
	err = list.Remove(10)
	fmt.Println(err)
	list.Print()

	// Remove last
	err = list.Remove(0)
	fmt.Println(err)
	list.Print()
}