In go, is this line creating a new empty map with string as key and value?

keys := []string{}

In go, is this line creating a new empty map with string as key and value?

No, that's creating an empty string slice.

This is an empty map with string as key and value:

keys := map[string]string{}

If you don't know what is the type, you can always check using reflect package:

package main

import (
    "fmt"
    "reflect"
)

func main() {
     keys := []string{}
     fmt.Println(reflect.TypeOf(keys))
     fmt.Println(reflect.TypeOf(keys).Elem())
}

Output:

[]string
string

Which means an empty slice of string.

Another eg to check the types inside the slice:

keys := []string{}
anotherKeys := []map[string]string{}

fmt.Println("keys: ", reflect.TypeOf(keys).Elem())
fmt.Println("anotherKeys: ", reflect.TypeOf(anotherKeys).Elem())

Output:

keys: string
anotherKeys: map[string]string

NB:
Elem()

No, []string is a slice of strings.

If you want an empty map with strings as the type for both keys and values, then map[string]string would be the correct type. Try the following example code in the Playground to see it for yourself:

package main

import (
	"fmt"
	"reflect"
)

func printKind(i interface{}) {
	fmt.Printf("Kind of %#v: %s\n", i, reflect.TypeOf(i).Kind())
}

func main() {
	emptySlice := []string{}
	printKind(emptySlice)

	emptyMap := map[string]string{}
	printKind(emptyMap)
}