if

  1. package main
  2. import "fmt"
  4. func main() {
  5.     a := 10
  6.     if a < 20 {
  7.         fmt.Println("a small then 20 /n")
  8.     }
  9.     fmt.Printf("a = %d", a)
  10. }

if … else

  1. package main
  2. import "fmt"
  4. func main() {
  5.     a := 10
  6.     if a < 20 {
  7.         fmt.Println("a smaller than 20 \n")
  8.     }
  9.     else {
  10.         fmt.Println("a biger than 20 \n")
  11.     }
  12.     fmt.Printf("a = %d", a)
  13. }

if 嵌套

  1. package main
  2. import "fmt"
  4. func main() {
  5.     a := 10
  6.     b := 20
  7.     if a < 20 {
  8.         if b == 20 {
  9.             fmt.Println("a smaller than 20 \n")
  10.         }
  11.     }
  12.     else {
  13.         fmt.Println("a biger than 20 \n")
  14.     }
  15.     fmt.Printf("a = %d", a)
  16. }

switch

  1. package main
  2. import "fmt"
  4. func main() {
  5.    grade := "B"
  6.    marks := 90
  8.    // 写法一
  9.    switch marks {
  10.       case 90: grade = "A"
  11.       case 80: grade = "B"
  12.       case 50,60,70 : grade = "C"
  13.       default: grade = "D"  
  14.    }
  16.    // 写法二
  17.    switch {
  18.       case grade == "A" :
  19.          fmt.Printf("优秀!\n" )     
  20.       case grade == "B", grade == "C" :
  21.          fmt.Printf("良好\n" )      
  22.       case grade == "D" :
  23.          fmt.Printf("及格\n" )      
  24.       case grade == "F":
  25.          fmt.Printf("不及格\n" )
  26.       default:
  27.          fmt.Printf("差\n" );
  28.    }
  29.    fmt.Printf("你的等级是 %s\n", grade );      
  30. }

select（暂时看不懂