The Type Switch is the best way to check a variable’s type at runtime. The Type Switch evaluates variables by type rather than value. Each Switch contains at least one case, which acts as a conditional statement, and a default case, which executes if none of the cases are true.
For example, you could create a Type Switch that checks if interface value i contains the type int or string:
1234567891011121314151617181920
package main
import "fmt"
func do(i interface{}) {
switch v := i.(type) {
case int:
fmt.Printf("Double %v is %v\n", v, v*2)
case string:
fmt.Printf("%q is %v bytes long\n", v, len(v))
