Golang顺序输出map

golang中map每次输出时顺序都不一致，在某些情况下甚至需要按顺序输出map。那么如何做到顺序输出呢？

1. map每次输出结果都不一致

package main

import (
	"fmt"
	"sort"
)

func main() {
	mp := make(map[string]string)
	mp["beijing"] = "beijing"
	mp["tianjin"] = "tianjin"
	mp["shanghai"] = "shanghai"
	mp["chongqing"] = "chongqing"
	mp["guangdong"] = "guangzhou"
	mp["jiangsu"] = "nanjing"
	mp["zhejiang"] = "hanzhou"

	for key, value := range mp {
		fmt.Println(key, " ----> ", value)
	}

	fmt.Println("second output")
	for key, value := range mp {
		fmt.Println(key, " ----> ", value)
	}
}

两次输出打印结果不一致，如下输出结果为：

chongqing ----> chongqing
guangdong ----> guangzhou
jiangsu ----> nanjing
zhejiang ----> hanzhou
beijing ----> beijing
tianjin ----> tianjin
shanghai ----> shanghai
second output
chongqing ----> chongqing
guangdong ----> guangzhou
jiangsu ----> nanjing
zhejiang ----> hanzhou
beijing ----> beijing
tianjin ----> tianjin
shanghai ----> shanghai

2. 顺序输出map
   实现顺序输出map，首先需要获取map中所有key，然后将key排序，最后按排序后key输出map。

package main

import (
	"fmt"
	"sort"
)

func main() {
	mp := make(map[string]string)
	mp["beijing"] = "beijing"
	mp["tianjin"] = "tianjin"
	mp["shanghai"] = "shanghai"
	mp["chongqing"] = "chongqing"
	mp["guangdong"] = "guangzhou"
	mp["jiangsu"] = "nanjing"
	mp["zhejiang"] = "hanzhou"

	for key, value := range mp {
		fmt.Println(key, " ----> ", value)
	}

	fmt.Println("second output")
	for key, value := range mp {
		fmt.Println(key, " ----> ", value)
	}

	fmt.Println("sort output")
	keys := []string{}
	for key, _ := range mp {
		keys = append(keys, key)
	}
	sort.Strings(keys)
	for _, key := range keys {
		fmt.Println(key, " ----> ", mp[key])
	}
	return
}

排序后输出结果为按key排序结果

chongqing ----> chongqing
guangdong ----> guangzhou
jiangsu ----> nanjing
zhejiang ----> hanzhou
beijing ----> beijing
tianjin ----> tianjin
shanghai ----> shanghai
second output
chongqing ----> chongqing
guangdong ----> guangzhou
jiangsu ----> nanjing
zhejiang ----> hanzhou
beijing ----> beijing
tianjin ----> tianjin
shanghai ----> shanghai
sort output
beijing ----> beijing
chongqing ----> chongqing
guangdong ----> guangzhou
jiangsu ----> nanjing
shanghai ----> shanghai
tianjin ----> tianjin
zhejiang ----> hanzhou