切片周围的包装纸正在做奇怪的事情

I am probably wasting my time implementing this, but I am looking for a way to push/pop to a slice more easily, so I have this:

package h

import (
    "sync"
    log "github.com/sirupsen/logrus"
)

type List struct {
   internalList []interface{}
    mux sync.Mutex
}


func MakeList(l []interface{}) List{
    return List{l, sync.Mutex{}}
}


func (l List) Add(args ...interface{}) List{
    l.mux.Lock()
    l.internalList = append(l.internalList, args...)
    log.Info(l.internalList)
    l.mux.Unlock()
    return l;
}

func (l List) Push(v interface{}) List {
    l.mux.Lock()
    l.internalList = append(l.internalList, v)
    log.Info("internal:",l.internalList);
    l.mux.Unlock()
    return l;
}


func (l List) Pop() interface{}{
    l.mux.Lock()
    length :=len(l.internalList);
    log.Info("the length is:", length)
    if length < 1 {
        return nil;
    }
    last := l.internalList[length-1]
    l.internalList = l.internalList[:length-1]
    l.mux.Unlock()
    return last;
}

func (l List) GetLength() int {
    return len(l.internalList);
}

func (l List) Shift() interface{} {
    l.mux.Lock()
    if len(l.internalList) < 1 {
        return nil;
    }
    first := l.internalList[0];
    l.internalList = l.internalList[1:]
    l.mux.Unlock()
    return first;
}

func (l List) Unshift(v interface{}){
    l.mux.Lock()
    l.internalList = append([]interface{}{v}, l.internalList...)
    l.mux.Unlock()
}

func (l List) GetValue() []interface{}{
    return l.internalList
}

and then I use it like so:

package main

import (
    "github.com/sirupsen/logrus"
    "huru/h"
    "huru/utils"
)

func main(){

    x := h.List{}
    x.Push(3)
    logrus.Info("value:",x.GetValue())
    logrus.Info("len:",x.GetLength());
    logrus.Info(x.Pop());


}

but the weird thing is I get this:

INFO[0000] internal:[3]                                 
INFO[0000] value:[]                                     
INFO[0000] len:0                                        
INFO[0000] the length is:0                              
INFO[0000] <nil>

I have no idea why 3 gets added to the slice, but then the slice length mysteriously goes to zero and when I pop() I get nil. Anybody know why that's happening?

Given the existing answer, I am wondering if there is a difference between:

func (l *List) Add(args ...interface{}) *List {
    l.mux.Lock()
    l.internalList = append(l.internalList, args...)
    log.Info(l.internalList)
    l.mux.Unlock()
    return l;
}

func (l *List) Push(v interface{}) *List {
    l.mux.Lock()
    l.internalList = append(l.internalList, v)
    log.Info("internal:",l.internalList)
    l.mux.Unlock()
    return l
}

and

func (l *List) Add(args ...interface{}) List {
    l.mux.Lock()
    l.internalList = append(l.internalList, args...)
    log.Info(l.internalList)
    l.mux.Unlock()
    return *l;
}

func (l *List) Push(v interface{}) List {
    l.mux.Lock()
    l.internalList = append(l.internalList, v)
    log.Info("internal:",l.internalList)
    l.mux.Unlock()
    return *l
}

Since your methods are mutating the data, they need to use pointer receivers:

func (l *List) Push(v interface{}) List {
    ...
}

Otherwise, the state will be updated on the copy of the struct, and lost after that.