package main
import (
   "fmt"
)
func main() {
   m := make(map[string]int)
   m["mukul"] = 10
   m["mayank"] = 9
   m["deepak"] = 8
   for key := range m {
      if key == "naina" {
         fmt.Println("Key named naina exists in the map")
      }
   }
   fmt.Println("No key named naina is present in the map")
   fmt.Println(m)
}

No key named naina is present in the map
map[deepak:8 mukul:10 mayank:9]

package main
import (
   "fmt"
)
func main() {
   m := make(map[string]int)
   m["mukul"] = 10
   m["mayank"] = 9
   m["deepak"] = 8
   fmt.Println(m)
   if _, ok := m["naina"]; ok {
      fmt.Println("The key exists in the map")
   } else {
      fmt.Println("No key named naina in the map")
   }
}

map[mukul:10 mayank:9 deepak:8]
No key named naina in the map