參考文檔：

https://www.cnblogs.com/double12gzh/p/13621445.html

有限狀態(tài)機（FSM）是一個抽象的機器，任何時刻該機器都處于某個狀態(tài)，且狀態(tài)總數(shù)有限。該機器可以根據(jù)輸入，從一個狀態(tài)轉(zhuǎn)換到另一個狀態(tài)中。
三個關(guān)鍵要素：初始狀態(tài)，可能狀態(tài)列表，觸發(fā)狀態(tài)變化的輸入

第一種實現(xiàn)思路

package main

import(
    "bufio"
    "fmt"
    "log"
    "os"
    "strings"
)

type State uint32

const (
    Locked State = iota
    Unlocked
)

const (
    dzToubi = "coin"
    dzTuiGan = "push"
)

func main() {
    state := Locked //初始狀態(tài)，鎖定
    prompt(state)
    
    reader := bufio.NewReader(os.Stdin)
    for {
        cmd, err := reader.ReadString('\n')
        if err != nil {
            log.Fatalln(err)
        }
        cmd = strings.TrimSpace(cmd)
        
        switch state {
            case Locked:
                if cmd == dzToubi {
                    fmt.Println("解鎖,請通行")
                    state = Unlocked
                } else if cmd == dzTuiGan {
                    fmt.Println("禁止通行，請先解鎖")
                } else {
                    fmt.Println("無效命令，請重新輸入")
                }
            case Unlocked:
                if cmd == dzToubi {
                    fmt.Println("門已開，投幣算是慈善了")                  
                } else if cmd == dzTuiGan {
                    fmt.Println("請通行，隨后道閘關(guān)閉")
                    state = Locked
                } else {
                    fmt.Println("無效命令，請重新輸入")
                }
        }
        
    }
    
}

func prompt(s State) {
    m := map[State]string {
        Locked: "關(guān)閉",
        Unlocked: "開通",
    }
    fmt.Printf("當(dāng)前閘機狀態(tài)為：[%s]，你下一步的動作是:[ coin | push ]\n", m[s])
}

優(yōu)化后的解法

package main

import(
    "bufio"
    "fmt"
    "log"
    "os"
    "strings"
)

type State uint32

const (
    Locked State = iota
    Unlocked
)

const (
    CmdCoin = "coin"
    CmdPush = "push"
)

type Turnstile struct {
    s State
}

func (p *Turnstile) ExecuteCmd( cmd string ) {
    //以當(dāng)前狀態(tài)和收到的命令構(gòu)成一個二元組
    tupple := StateCmdTupple{p.s, strings.TrimSpace(cmd)}
    
    //通過二元組查詢狀態(tài)轉(zhuǎn)換表，獲得一個轉(zhuǎn)換函數(shù)
    //本例中，這個表是通過map實現(xiàn)的，二元組是Key
    if f := StateTransitionTable[tupple]; f == nil {
        fmt.Println("無效命令，請重試")
    } else {
        f(&p.s)
    }   
}


type StateCmdTupple struct {
    s State
    c string
}

type TransitionFunc func(s *State)

var StateTransitionTable = map[StateCmdTupple]TransitionFunc {
    {Locked, CmdCoin}: func(s *State){
        fmt.Println("已解鎖，請通行。")
        *s = Unlocked
    },
    {Locked, CmdPush}: func(s *State){
        fmt.Println("禁止通行，請先投幣。")
    },
    {Unlocked, CmdCoin}: func(s *State){
        fmt.Println("多投的幣會捐給國家。")
    },
    {Unlocked, CmdPush}: func(s *State){
        fmt.Println("請盡快通行，通過后閘機鎖定。")
        *s = Locked
    },
} 

func prompt(s State) {
    m := map[State]string{
        Locked: "鎖定",
        Unlocked: "解鎖",
    }
    fmt.Printf("閘機當(dāng)前的狀態(tài)是: [%s], 請輸入命令（coin或push）\n", m[s])
}


func main() {
    machine := &Turnstile{Locked}
    prompt(machine.s)
    
    r := bufio.NewReader(os.Stdin)
    for {
        cmd, err := r.ReadString('\n')
        if err != nil {
            log.Fatalln(err)
        }
        machine.ExecuteCmd(cmd)
    }
}