Question

How does one delete data from a map in Go? For example, having

m := map[string]string{ "key1":"val1", "key2":"val2" };

I want to make m drop the “key1” without copying the entire map by iterating over its keys (which could get big in some uses). Is it enough to assign a nil value to “key1”, or will that still keep the key in the map structure with an assigned value of nil? That is, if I later iterate over the keys of the map, will “key1” appear?

Answer 1

Deletion of map elements

The built-in function delete removes the element with key k from a map
m.

delete(m, k)  // remove element m[k] from map m

For example,

package main

import "fmt"

func main() {
    m := map[string]string{"key1": "val1", "key2": "val2"}
    fmt.Println(m)
    delete(m, "key1")
    fmt.Println(m)
}

Output:

map[key1:val1 key2:val2]
map[key2:val2]