fileName := "a.txt"
contents ,err := ioutil.ReadFile(fileName)
    if err != nil{
       fmt.Println("文件不存在")
 }else{
   fmt.Printf("%s\n",contents)
 }

fileName := "a.txt"
if contents ,err := ioutil.ReadFile(fileName);err!=nil{

 fmt.Println("文件不存在")

}else{

 fmt.Printf("%s\n",contents)

}

go 语言的switch 默认会加break

var c = 2
 switch c {
 case 1 :
   fmt.Print(c)
 case 2:
   fmt.Print("hello")
 case 3:
   fmt.Print("world")
 default:
    fmt.Println("this is the end")

switch 后面可以不跟表达式

var score = 80